Cook bacon in fry pan until crisp. Drain and set pieces aside. Wash and dry fry pan. Place two pieces of cheese on four of the pieces of bread and top each with two slices of tomato & two slices of bacon. Sprinkle with salt and pepper if desired. Top each sandwich with the leftover bread slices and spread ½ tablespoon of mayonnaise on the top of each sandwich. Put the sandwiches mayonnaise side down in fry pan (may require 2, or do 2 batches of sandwiches) and cook over medium heat until bottom is browned. Spread the remaining mayonnaise on the sandwiches and flip. Cook until golden brown. Transfer to plates and cut in half diagonally. SERVES 4