Recipe adapted from Emeril Lagasse   Tuna Melts! Ingredients 4 (6-ounce) cans solid white tuna packed in water, drained 1/4 cup plus 1 tablespoon mayonnaise, plus more for spreading 1/4 cup finely chopped red onion 1 tablespoon plus 1 teaspoon capers, drained 1 tablespoon plus 1 teaspoon freshly ground black pepper 1 tablespoon fresh lemon