Insalata di tonno e fagioli is a traditional salad hailing from Italy. The salad is usually made with a combination of red onions, olive oil, salt, pepper, cannellini beans, and tuna (usually the one that's canned in olive oil). The onions are thinly sliced, covered with cold water, seasoned with salt, and left to sit for an hour to make them sweeter and more digestible.