Romesco (Catalan pronunciation: [ruˈmɛsku]) is a tomato-based[1] sauce that originated from Valls, province of Tarragona, in Catalonia, Spain.

[2] It is typically made from any mixture of roasted tomatoes and garlic, toasted almonds, pine nuts, and/or hazelnuts, olive or sunflower oil, and nyora peppers (capsicum annuum, a sun-dried, small, round variety of red bell pepper).

When touring Catalonia, though, Clark discovered that there was no single correct recipe and encountered several variations.

Clark described romesco as "a rich and piquant purée made from sweet dried Spanish peppers along with tomato, garlic, almonds, vinegar, and oil, pounded with breadcrumbs as a binder."

The charred layer is then removed, and the tender part of the onion may be dipped into the sauce.