La Mejillonera

"There are two things locals go to La Mejillonera for: patatas bravas (a native Spanish tapa made of fried potatoes topped with a warm sauce, which differs depending on the region of Spain you’re on, but usually has a mayonnaise component to it) and mussels. There are a few different sauces for the shellfish, but the mildly spicy tomato dressing is definitely the way to go."

— Forbes