4 cans Chunk light Tuna in Water Tuny® (5 oz each) 4 crispy corn tostadas ½ cup mayonnaise (optional, for creaminess) 1 ripe tomato, diced ¼ red onion, finely minced ½ cup shredded lettuce 6 to 8 black olives, sliced Salt and freshly ground black pepper (to taste) Fresh lime juice (to taste)