Imagine you're an American traveling abroad, and one day you go to a restaurant with American-style hot dogs on the menu. You order one, out of curiosity, and receive a wiener stuffed into a crusty roll, topped with Dijon mustard and quick-pickled slaw. You can clearly map all of the components to the original it's trying to emulate, and the result might even taste good, but every part of your mouth is screaming, Hoo boy, this is all wrong!
How to Make Romesco Sauce
That, I imagine, is what Spaniards might think eating their nutty romesco sauce in the States. In place of oven-roasted tomatoes, raw ones are routinely substituted. Instead of the dark and concentrated flavor of dried peppers, big, sweet roasted fresh red bell peppers find their way into the recipes. Then people get creative, adding raw onion and a spice bazaar's worth of seasonings. The result looks like romesco sauce, and it kinda tastes like it, but it's not quite right...
Or maybe it's not that simple. Even in Spain, romesco comes in many forms, and each cook has their own way of making it. To add to the confusion, "romesco" is often used to describe both the sauce itself and a class of dishes flavored with the sauce, including a pretty spectacular-looking fish stew.*
*Run a search for romesco de peix, the Catalan name, to see what I'm talking about.
Romesco is also often conflated with a very similar sauce called salvitxada (which in turn is also known as salsa de calçots), served as part of the calçotada, a grilled spring-onion feast. There certainly seems to be a lot of leeway around how it can be made.
Let's take a closer look at the sauce and how to make it. Then you can decide for yourself where to get creative and where to stick to tradition.
What Is Romesco Sauce?
Romesco sauce comes from Tarragona, a Catalonian city just south of Barcelona on Spain's northeastern coast. Its base ingredients usually include nuts—often almonds and/or hazelnuts—tomatoes, dried peppers, garlic, bread, olive oil, and vinegar, all mashed or processed into a paste.
It's more versatile than one might imagine. It goes with just about anything—meats, poultry, fish, vegetables, on sandwiches, dolloped into bowls of soups, spread on toasted bread. It can be made thick or thin, chunky or smooth, spicy or mild; it can be rich and oily or fruity and bright.
Stirred into stews and braising liquids, it brings all the flavor you could possibly want. You can put it on pasta, toss it with rice, thin it with oil and vinegar and use it as a dressing for bitter greens; heck, you can probably brush your teeth with it. If the old-school pitchmen of Atlantic City had ever gotten their hands on it, this is the point where they'd say, "But wait, there's more!" And then they'd reel off another 30 ideas for how to use it.
In short, it's a sauce you want in your rotation.
The First Fork in the Romesco Road: Tomatoes and Garlic
When making romesco, the first thing you want to consider is how to handle your tomatoes and garlic. Many American recipes just assume you'll use raw fresh tomatoes and pungent raw garlic. That's not a safe assumption.
Most Spanish recipes call for roasting the tomatoes and garlic in the oven first to drive off excess liquid, deepen their flavor, and punch up their sweetness. This allows you to pack more tomato flavor into the sauce without turning it into a tomato soup. It also makes it easier to slip the skins off the tomatoes, which is good, since removing the skins improves the texture of the sauce.
The garlic, meanwhile, takes on a much softer, sweeter flavor when roasted. Roasting means you can add more of it without overwhelming the romesco, though a clove or two of raw garlic tossed in for good measure isn't a bad idea. In fact, that's the combination I settled on for my recipe: taking advantage of the softening effects of roasting, but also incorporating a little raw garlic for punch.
The Second Fork in the Romesco Road: The Pepper Component
Most people who know romesco know that it contains pepper, but many mistakenly think that pepper is a roasted red bell pepper. It's not. The pepper used for romesco is a dried one, either the ñora pepper or, according to some sources, the choricero pepper.
Of course, those Spanish pepper varieties aren't easy to get here, which is why the bell pepper became a popular substitute. Roasting a bell pepper does add some of the darker notes that the dried peppers offer, and romesco sauces made with bell peppers can taste good. But anyone who knows what the original sauce, made with those dried peppers, tastes like, knows that bell pepper doesn't really play the part well enough. A better route is to use some kind of dried pepper.
You can buy ñora peppers at Spanish specialty stores, or online at sites like La Tienda. I think it's worth it. The ñoras add a depth that the red bell pepper simply can't. They taste molasses-y, but without a strong sweetness, and there's a bitterness that cuts through everything else. It's a complex flavor that brings the romesco fully into focus.
If you can't find ñora peppers, your best option for a substitute is Mexican ancho chile peppers. I did a side-by-side test, and, while the sweeter flavor and mild heat of anchos make them less than an exact match, they come a lot closer than red bell peppers do.
Preparing the peppers involves first soaking them in boiling-hot water to rehydrate and soften the flesh, then stemming and seeding them, and finally scraping the tender meat off the papery skin.
The Third Fork in the Romesco Road: Nuts, Nuts, Nuts
Now's your chance to...go nuts. Almonds and hazelnuts are the most common nuts in a romesco sauce, and you should feel free to experiment with what you like best, whether that's an all-almond sauce, an all-hazelnut sauce, or some kind of mix. No matter what combination you use, you'll want to toast the nuts to bring out their flavor, and remove their skins to keep them from making the sauce gritty.
Tools of the Romesco Trade
I have a mortar and pestle obsession, and romesco sauce just adds to my love of them. A mortar and pestle is the tool traditionally used to make romesco, and I'd argue it's what you should use today if you want a romesco with the most character, in both its texture and its flavor. The sauces I've made with my mortar and pestle have been sweeter, more complex, and more delicious than those made with a blender or food processor. The texture is also more rustic, which I like as well.
The flavor improvements I noticed from the mortar and pestle are likely due to how the tool works. Unlike the spinning blades of a blender or food processor, which chop the ingredients into smaller and smaller bits, a mortar and pestle crushes them, breaking open the plant cells and releasing more of what's trapped inside. This generally translates into better flavor.
That said, you don't have to use a mortar and pestle. This is a forgiving sauce, and it comes out great even with those chippity-choppity appliances of modern convenience.
And that's what's so great about romesco—it's open to interpretation. But to interpret something, you first need to understand the basics, so that your decisions are informed and deliberate. Use fresh tomatoes and roasted red bell peppers if you want, but do it knowing there are other options, not just because that's what all the Americanized recipes are telling you.