When it comes to tomato sauce, we here at Serious Eats have you covered,* but I noticed recently that we hadn't yet offered a recipe for a tomato coulis. It's about as simple as tomato sauce gets—essentially just a puree made from fresh tomatoes, which you can then go on to use as you wish.
*There's my laborious but insanely good sauce made from fresh tomatoes. And then there's Kenji's oven-roasted red sauce, which is just as much work and just as wonderful. To help save you some time, I also created a much simpler marinara that's a heck of a lot less work, but still sterling.
When making coulis, most of the year I generally prefer to puree canned whole tomatoes, since canned tomatoes are riper when picked than your average supermarket tomato. The only challenge is that canned tomatoes taste very cooked, and sometimes you want a fresher tomato flavor. Other times, you have an overabundance of great fresh tomatoes and want to make the most of them (think end of summer at the farmers market).
Looking at existing recipes, I found many ways to make a tomato coulis. Some people peel and seed the tomatoes, dice them, then cook them just enough to remove excess water, then puree them. Others prefer to skip the peeling and seeding steps, instead opting to cook them—seeds, skins, and all—and strain them after. And then there are the folks who seed and peel the tomatoes, salt them to remove excess moisture through osmosis, and then finally puree the salted tomatoes while they're still raw.
Of course, you'll also find tomato coulis that are more complicated, with aromatic vegetables or splashes of vinegar and pinches of sugar. I decided not to go down this road, since that ventures more into true sauce territory. Think of a tomato coulis as you would a meat stock: Once you have a good basic method for making it, it becomes the base for many other dishes and sauces down the line.
I played around with many of the most common methods—peeling, seeding, cooking, pureeing, and salting—to see which approach I preferred. What I've ended up with are two recipes, one for a quick-cooked tomato puree, the other for a raw sauce with an especially bright, fresh flavor.
Cooked Tomato Coulis
For a cooked coulis, I strongly prefer leaving the skins and seeds on during cooking and straining them out afterwards. Tomato seeds and, more specifically, the jelly they're suspended in, have a lot of flavor, so it makes sense that including all of that during the cooking step would lead to a coulis with better, more rounded flavor. Thankfully, it's also easier to make this way.
To make it, I dice tomatoes, then toss them in a pot and set it over moderate heat, stirring frequently. The tomatoes quickly begin dumping out their water as they heat up.
I simmer the tomatoes until most of the excess liquid has cooked off, then transfer them to a strainer or food mill.
We don't have a food mill in the Serious Eats test kitchen (mental note: add a food mill to our equipment shopping list), so for this batch I strained the tomatoes manually, pushing them through a mesh strainer with a wooden spoon. A scraping motion is more effective for getting the flesh to pass through than just pushing down.
If you have a food mill or an electric tomato strainer, it'll make this process even easier.
The resulting coulis may be a little coarse, depending on the fineness of your strainer. You can either leave it like that if you don't mind a little texture, or you can pass it through an even finer strainer to get a smoother result.
Raw Tomato Coulis
For a raw tomato coulis, we'll use a blender instead of a pot. This means we'll have to remove the skins and seeds first so that we don't blend them into the sauce—they can add unwanted flavors if not strained out. Plus, because we're not cooking this coulis, we need to remove some moisture to prevent wateriness in the finished puree, which also means the seeds need to go.
To peel the tomatoes, I cut out the stem end and score an X into the skin with a sharp knife. Then I drop them in boiling water until the skins just start to show signs of coming loose around the score marks (just about 30 seconds to a minute). Finally, I transfer the tomatoes to an ice bath to shock them and stop the cooking; this will help loosen the skins even more. You should be able to just peel them right off with your hands.
Then I quarter the tomatoes lengthwise and scoop the seeds out with my fingers.
I dice the remaining tomato flesh, transfer it to a mesh strainer set over a bowl, and sprinkle it liberally with salt, which will draw out moisture. After about 30 minutes to an hour, I puree the pulp with a blender. The puree has a very bright, fresh flavor, like gazpacho—but without any of the other ingredients, obviously.
Once again, you can pass this puree through a really fine strainer if you want a smoother texture, or leave it as is.
From there, use either coulis as you wish. The cooked one can be incorporated into any cooked dish or used to make a full-fledged sauce by combining it with aromatics like onion, garlic, and herbs. The raw one, on the other hand, would be great tossed with pasta, olive oil, and fresh basil, or spread onto crusty bread and drizzled with olive oil. Plus, since both types freeze really well, they're the kind of thing you can make in large batches in the summer and then defrost long after tomato season is over.
And with that, I think we really do have every major tomato sauce need covered.