This sauce is a simple rendition of Catalan romesco, a blend that traditionally includes roasted tomatoes, nuts, garlic, ñora chilies, olive oil and bread for thickening. In our six-ingredient version, we add smoked paprika and woodsy sherry vinegar—two ingredients that give the sauce a decidedly Spanish flavor and aroma. It’s a delicious accompaniment to grilled vegetables and grilled or seared steaks, lamb or chops. Or smear it onto sandwiches or include it in a grilled cheese.