Andalusian Potato Salad

You’d be crazy to go to an Andalusian tapas bar and not order papas aliñas (marinated potatoes). These are shallow bowls of diced yellow potatoes tossed with sweet white onions, green peppers, and sometimes tomato and tuna, then generously bathed with good olive oil and sherry vinegar. Like many a classic tapa, it is a simple but fundamental dish on which a bar’s reputation depends. Bar Casablanca, a venerable Seville tapas counter, has my favorite version—and many sevillanos