In a bowl, combine the tuna, mayonnaise, and black pepper. Spread this mixture over toast, and top with strips of bacon, slices of avocado, and cheese. Place sandwiches on a baking sheet.
Place a baking sheet with sandwiches in a preheated oven and bake the tuna sandwiches for about 2 minutes, until the cheese melts. Serve the tuna sandwiches immediately.