The Food Lab: The Secret to Perfect Beef Tenderloin? The Reverse Sear Strikes Again

The Food Lab

Unraveling the mysteries of home cooking through science.

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Beef tenderloin is best when it's fully medium-rare to rare from edge to center. [Photographs: J. Kenji López-Alt, unless otherwise noted]

When it comes to celebratory roasts, especially at the holidays, prime rib has always been my meat of choice, with its full-flavored fattiness and primal ribs. But tenderloin (or "filet mignon," if you want to be all fancy about it), the milder, more tender cut from the other side of the rib cage, has a lot of good things going for it, too. For one thing, it's by far the most tender cut on the steer. No matter how you cook it, it's gonna be soft enough to cut with a fork, and if you nail it just right, it gets a melt-in-your-mouth, almost buttery texture, all with a minimal amount of fat. It's also very easy to carve and serve. Since it has a nice cylindrical shape and no bones, you don't really have to worry about mastering fancy carving skills or finding the grain or anything like that. Just slice medallions and serve.

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If primal and carnal is your bag, then prime rib should be your roast of choice. But if you want to go subtle, elegant, and refined? Put a tenderloin on your table this year.

That said, tenderloin is not without its problems, and almost all of them boil down to its low fat content. First off, there's this:

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Most of the distinctive flavor in meat comes from fat, and, with only trace amounts of marbling, tenderloin is just about as nondescript as beef comes. That's why most tenderloin recipes you'll see come with some kind of big, punchy flavor added, whether it's in the form of a bacon wrap, a pepper crust, or a high-impact sauce.

Lack of fat can also make cooking it more difficult. See, fat is an insulator (don't believe me? Just ask a whale or a walrus), and, as such, it slows down the rate of heat transfer. This means that, given two pieces of meat of the same size and shape, the one with less fat will cook faster.

So why is this a problem? you might ask. Isn't cooking faster a good thing? Back up. Faster cooking also comes with some baggage: The faster a piece of meat cooks, the larger the temperature gradient within that piece of meat. This means that with a lean tenderloin, it's very easy to end up with a roast that is well-done in the outer layers while the center barely hits medium-rare, like this:

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[Image: Shutterstock]

To make this problem even worse, without the benefit of fat, well-done lean tenderloin ends up dry and cottony. So the question is, how do you roast a tenderloin so as to maximize the amount of medium-rare meat, while also adding plenty of flavor?

Let's first talk a bit about how well-done you should actually be aiming for.

A Rare Case

I used to be one of those "wave the steak in the direction of the fire and serve it to me" types. The rarer, the better. But when I actually started thinking critically about what was in my mouth, rather than letting whatever minor sense of machismo I had get the better of me, I realized that rarer does not always equal better, and I'm willing to bet that anybody who currently thinks so could be convinced otherwise.

These days, I firmly believe that when you're cooking red meat, the degree of doneness to which you cook it should be directly related to its fat content. Rich, fatty cuts, like prime-grade prime rib, are better cooked to at least medium-rare, and often even up to medium—hot enough that the plentiful intramuscular fat can start to soften, spreading its flavor and its lubrication over your mouth.*

* In fact, in blindfolded taste tests I conducted, even avowed rare-meat-eaters more often than not picked the medium-rare prime rib or the medium prime rib over the rare as the best-tasting. This also may explain why the French, with their very lean beef, tend to prefer their meat cooked very rare, while Americans, with their extra-fatty meat, veer toward medium. Nobody can explain why the Brits cook their lean beef beyond well-done.

A lean tenderloin, on the other hand, has no intramuscular fat, so go beyond medium-rare at all and you're just drying it out. For tenderloin, edge-to-edge pink, with perhaps even a spot of translucent rare meat in the very center, is the way to go. And, of course, we still want a really nice dark crust on the exterior for flavor and texture.

Making the Cut

Before we get to the oven, though, we need to first figure out what cut of meat we're working with. A full tenderloin is a big chunk of meat, about four to five pounds. Because a whole tenderloin has an uneven shape, with a thin, tapered tail and a fat bulb on the other end, you'll need to fold that thinner end back and tie it into place to get it to cook evenly.

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This is fine if you've got a large party of eight to 12 to feed, but for a smaller group of four to six, you'll want to use a center-cut tenderloin, also known as a chateaubriand.

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This is the center section of the tenderloin, and it has a smooth, even, cylindrical shape that makes cooking it much simpler. (If you want to learn how to save some money by trimming a tenderloin yourself, check out our guide here.)

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Cooking it on its own can cause it to sag and turn misshapen as it cooks, so I always like to truss a tenderloin by tying it up at even intervals. Learning how to tie butcher's knots makes this very easy, though regular old square knots will work as well.

So how do you get there? Well, traditional recipes for tenderloin (and most steaks and roasts) call for first searing the meat at a high temperature, then finishing it off at a relatively low temperature. By this stage, we all know that the whole "sealing in the juices" thing is nothing more than a myth with no actual basis in reality, right? So, while the standard hot-then-cool method works okay, it actually works better if you do the process in reverse.

It's a thing called the reverse sear, a technique I developed while I was working at Cook's Illustrated (and if you've already heard me talk about it a million times, you may want to skip ahead a bit). These days, I use it for everything from prime rib to pan-seared steaks to pork chops—any time I want perfectly evenly cooked meat and a great crust.

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When you start the process by placing the raw meat on a rack in a low-temperature oven (in this case, I went with 225°F—the lowest temperature my oven could reliably hold) and slow-roasting it until the center hits just a few degrees below your desired final serving temperature (a serving temperature of 125°F for rare or 130°F for medium-rare is what I shoot for), you end up with a piece of meat that has a very small temperature gradient. The meat will be almost perfectly cooked from edge to edge.

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Low-and-slow cooking also gives you a larger window of time between that point at which the meat is perfectly cooked and the point when it's overcooked.

Once the meat is done, all you've got to do is put a sear on it. With a steak, I'll generally do that in a large skillet on the stovetop. If your tenderloin is small enough, you can do it the same way, basting it with butter, shallots, and thyme for extra flavor and richness. The added milk proteins in butter also help it to brown faster than oil does.

But what if it's too large to fit in a skillet, or you prefer to use the oven?

At first, I thought I could treat a tenderloin exactly how I treat my prime rib—just toss it in a 500°F (260°C) oven for a few minutes to sear the exterior. I tried it and ended up with barely browned meat and a big, fat layer of overcooked meat around the outer edges.

The problem, of course, is that fat content again. A prime rib has a nice thick layer of fat on its exterior that can help it brown faster and more evenly. It also cooks more slowly due to this insulation, so even with a 10-minute stay in a 500°F oven, you get barely any gray, overcooked meat under the surface. With a lean tenderloin, on the other hand, 10 minutes in a 500°F oven leads to a chunk of meat that's cooked beyond medium, almost all the way to the center!

So my goal was to figure out ways to speed up the browning process so that the tenderloin wouldn't have time to overcook. It took a two-pronged approach to get there.

You've Got to Dry to Get Brown

The first step to better browning is to realize that wet things don't brown. Because water evaporates at 212°F (100°C), until you've fully desiccated the surface of a piece of meat, it's very difficult to get it to rise beyond that temperature. On the other hand, browning reactions don't really take place in earnest until temperatures reach into the 350°F+ range (177°C and up).

Knowing this, I decided to pretreat my meat in two different ways: salting heavily, and a lengthy rest.

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Salting a piece of meat does more than give it flavor. It intrinsically alters its muscle structure. As salt dissolves in meat juices and works its way slowly into the meat, it dissolves a protein called myosin—one of the proteins responsible for the shrinkage that occurs when meat is heated. Visually, this change is quite apparent when you compare a piece of salted meat to a piece of fresh meat. Denatured proteins scatter light in a different way from intact ones, giving salted meat a deeper red, slightly translucent appearance, kind of like ham.

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A piece of meat that is salted for a prolonged period of time will shrink less and expel less moisture as it cooks. Less moisture expelled means less moisture to evaporate, which means more efficient browning. Since a thick roast can't really be seasoned internally until it's sliced and served, I like to salt my meat quite heavily around the edges.

Resting the meat after salting offers its own obvious advantage: partial dehydration of the exterior. As I talked about in this piece on dry-aging (or not, as the case may be), a steak that's been left to sit uncovered for a night or two on a rack in the fridge will develop a nice dry pellicle that will brown very fast.

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Combining the salting step with an overnight rest led to a roast that was extremely dry on the exterior after its initial slow roast:

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For the record, this is one of the few advantages that the oven-based reverse-sear method has over bag-and-water-based sous vide methods. While sous vide cooking allows for more precise temperature control, it also leaves the exterior of the meat very wet.

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Sous vide meat cooks very efficiently and evenly, but is harder to sear than slow-roasted meat.

This can make it harder to sear, which in turn can end up giving you more of an overcooked gray band than you'd like.

Once the whole tenderloin had been slow-cooked, I decided to try to bring some of the flavor and richness of the pan-seared version to the oven-roasted version, figuring that some browned butter might also help it brown faster while providing a lubricating and insulating layer of fat on the exterior.

To do it, I started by browning butter in a skillet, then added some sliced shallots and thyme.

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Next, I dumped that browned butter and the aromatics over my tenderloin, using a spoon to make sure every surface was coated, and pushing the shallots to the side so that the top of the meat was exposed.

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Finally, I parked the tenderloin under a preheated broiler. Because of the moisture-free surface and the already-hot browned butter, the roast started sizzling and crackling under the heat of the broiler almost immediately. Those sizzling sounds are good news.

A couple minutes and a few turns with the tongs later, and this beauty emerged from the oven:

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Would you look at that crust? Normally, I'd let a roast of this size rest for about 15 minutes in order to prevent it from leaking too many juices, but with slow-cooked meat, you really don't need to rest more than a couple of minutes before slicing and serving.

Ready for the moment of truth? I find myself holding my breath every single time I cut into a steak or a roast, even when my thermometer tells me that all is going to be well.

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Phew! It worked! Nicely browned crust, an ultra-tender center, and perfectly pink meat from edge to edge. You couldn't really ask for much more in a tenderloin.

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Okay, I suppose you could ask for a sprinkle of really nice, coarse sea salt and some minced chives. And perhaps a nice steak knife would be fitting. And if you really want to deck it out, some horseradish cream sauce, but we don't want to get too greedy, now do we?

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Or maybe we do. 'Tis the season, after all, am I right?