Vinegar gives boquerones en vinagre their defining marinade, which cures the small fish and gives the tapa its sharp flavor.
The dish uses fresh anchovies that are cleaned and filleted before being covered in vinegar. After marinating, they are commonly dressed with olive oil, garlic, and parsley. The finished fish are served chilled as a bright, acidic small plate.
The Spanish name means “anchovies in vinegar.” This distinguishes the preparation from boquerones fritos, in which anchovies are coated and fried. The two dishes use the same broad fish category but produce very different textures and flavors.
Because the fish is traditionally marinated rather than fully cooked by heat, food-safety practices are important. Modern preparation commonly includes freezing the fish beforehand to reduce parasite risk. That technical step does not change the dish’s defining ingredient: vinegar.