Romesco with Roasted Red Pepper and Almond

Romesco is the sauce that made me stop being frightened of nuts in savoury cooking. It is Catalan, the colour of old brick, and it tastes of toasted almond, sweet pepper and a sharp back-note of sherry vinegar that keeps the whole thing from turning heavy. The version most people meet is a smooth orange dip served with spring onions; the version worth making at home is a little coarser, a little smokier, and built around peppers charred black over a live flame until their skins blister and lift. That charring is the small change that gives this batch its depth — the sugars in the pepper flesh caramelise against the fire in a way that roasting alone never quite manages.

Where romesco comes from, and why it belongs to Tarragona

Romesco is native to Tarragona, the port city south of Barcelona, and its origins are tied to the fishermen who worked that stretch of the Catalan coast. The traditional account holds that fishermen made it aboard their boats to dress the day’s catch, pounding almonds, garlic, bread and the local dried peppers together in a mortar with oil and vinegar into something that would cling to grilled fish and travel well without spoiling. The sauce takes its name from the romesco pepper, a local variety, though the dried pepper most closely associated with it now is the small, round, sweet ñora, which is grown along the Mediterranean coast and dried whole.

The dish that made romesco famous beyond Catalonia is the calçotada, the great winter feast built around calçots — a type of sweet, elongated spring onion grown by banking earth up around the stems as they grow, the way you would blanch leeks. From late winter into early spring, Catalans gather to grill enormous quantities of calçots over vine cuttings until the outsides are charred to charcoal, then slide off the burnt layer, dunk the sweet white core into romesco and eat them messily with the head tipped back. It is a gloriously undignified way to eat, usually finished with grilled lamb and a lot of young red wine, and romesco is the thread that runs through the whole meal.

What gets lost in the export version is how variable romesco genuinely is. Every Catalan family and every restaurant has its own ratio, and the arguments over whether hazelnuts belong alongside the almonds, whether the bread should be fried or merely stale, and how much vinegar is too much, are exactly the kind of arguments I have about garlic. The one thing nobody disputes is that the sauce should taste of toasted nuts first and pepper second, with the tomato and garlic playing a supporting role underneath.

Why char the peppers, and what the nuts are actually doing

Roasting peppers in the oven gives you soft, sweet flesh, which is fine. Charring them directly over a flame gives you something better: the intense dry heat blackens and lifts the skin in a couple of minutes while the flesh underneath picks up a genuine smokiness from contact with the fire, before it has time to stew in its own steam. Once the blackened peppers go into a covered bowl, the trapped heat loosens the skins further, and they slip off in sheets under your thumb. Skip the resting-and-steaming step and you will spend twenty minutes picking at stubborn skin; give it the full ten minutes covered and it comes away almost on its own.

The nuts and bread are doing the structural work here, and understanding that is the difference between a sauce that holds together and one that splits into a puddle of oil. Ground toasted almonds and fried bread act as the thickener and the emulsifier — the starch in the bread and the finely ground nut particles trap the oil in suspension, the way egg yolk does in a mayonnaise, so the finished sauce stays thick and spoonable rather than weeping oil at the edges. This is why you blitz the almonds and bread to a rubble first, before adding anything wet: you want them broken down enough to do their job. Add the oil too fast at the end and the emulsion can break, leaving you with a greasy, grainy sauce; pour it in a thin, steady stream with the motor running and it comes together thick and glossy.

Toasting the almonds properly matters more than people expect. Raw almonds make a flat, milky sauce; almonds fried in oil until they are deep gold — well past pale, right to the edge of brown — bring the roasted, warm flavour that defines romesco. Watch them closely, because they go from perfect to burnt in under a minute, and burnt almonds turn the whole batch bitter with no way back.

The recipe

Makes about 400ml, enough for six as a sauce. Prep 20 minutes, cook 25 minutes, then rest.

Ingredients

• 2 large red romano or bell peppers
• 3 ripe tomatoes, halved
• 80g blanched almonds
• 1 thick slice stale country bread, crust removed
• 3 garlic cloves, unpeeled
• 2 dried ñora peppers, or 1 tsp smoked paprika
• 120ml extra-virgin olive oil, plus more for frying
• 2 tbsp sherry vinegar
• 1 tsp flaky salt, plus more to taste
• A pinch of cayenne (optional)

Method

Soak the ñora peppers in just-boiled water for 20 minutes, then scrape out the soft flesh and discard the skins. Char the fresh peppers over a flame until blackened all over, steam them covered for 10 minutes, then peel, deseed and tear into strips. Fry the almonds in a little oil until deep gold and lift out; fry the bread until crisp; soften the unpeeled garlic in the same pan, then peel. Roast the tomato halves until collapsed and slip off the skins. Blitz the almonds and bread to a coarse rubble, then add the peppers, tomato, garlic, ñora flesh or paprika, vinegar, salt and cayenne and blitz to a rough paste. With the motor running, stream in the olive oil until thick and emulsified. Taste, adjust the salt and vinegar, and rest for 30 minutes before serving.

Tips, substitutions and storage

The texture is a matter of taste, and worth deciding on deliberately. For dunking calçots or spring onions, leave it coarse, with visible flecks of almond. For coating grilled fish or spooning over roast vegetables, blitz it longer until nearly smooth. It thickens as it sits, so if it stiffens too much in the fridge, loosen it with a teaspoon of warm water or a little more oil.

If you can’t find ñora peppers, a good sweet smoked paprika does a fair job of standing in for their gentle, raisiny heat, and since you are already charring the fresh peppers, the smokiness carries through well. Avoid hot smoked paprika unless you want the sauce to lean fiery; romesco should sit warm rather than sharp on the tongue. Hazelnuts, toasted and skinned, can replace up to half the almonds for a rounder, slightly sweeter version closer to some Barcelona recipes.

Romesco keeps in a sealed jar in the fridge for up to a week, with a thin film of oil poured over the top to seal it from the air — the flavour deepens over the first day or two as the garlic mellows and the vinegar rounds out, much the way a good salsa verde improves after a short rest. Bring it back to room temperature before serving, as fridge-cold blunts the nuttiness. It does not freeze well; the emulsion separates on thawing and the texture turns grainy.

What to eat it with

Its classic home is on charred alliums and grilled fish, but romesco is one of the most useful sauces to have in the fridge. Spoon it over roast cauliflower or charred asparagus, fold it through warm new potatoes, or use it as a bed under grilled prawns. It makes a superb sandwich spread with cold roast chicken, and a spoonful stirred into a bowl of white beans turns them into a proper lunch. For a spread of dips and cold sauces, it sits happily alongside a herby, punchy piri-piri sauce — one smoky and mellow, the other bright and hot, which is exactly the contrast a table of small plates wants. Make a double batch when peppers are cheap in late summer; it disappears faster than you expect.