Catalan Vinaigrette

This is one of the three sauces that invariably accompany grilled meats and seafood in Barcelona (the others are romesco and alioli, cousin of the Provençal aioli, a simple garlic-spiked mayonnaise). If you think of vinaigrette as too delicate a sauce to stand up to a steak, try this caper, shallot, and pickle–flavored version. You’ll be pleasantly surprised.