When Francisco Santos opened this tiny bar next to La Mezquita in 1966, he knew he needed something to set his place apart. That something became a massive tortilla Española, or potato omelet, that has been called the best in Spain. The creamy slices attract crowds of patrons who spill out into the street. Among the other tapas, we like the tuna topped with roasted red peppers and the bowl of salmorejo with slices of bread. This is a cash-only establishment.