This tuna melt tastes incredibly rich and uses no mayo. It's a versatile recipe too. You can change the type of bread or cheese, spice it up or down, or even switch it to salmon instead of tuna, and it always comes out great. The lime juice "pre cooks" the tuna and makes it seem creamier, so you don't need any mayonnaise. It makes 4 sandwiches if your bread slices are small, but only 2 or 3 larger sandwiches if you use big slices of bread.