Cook the bacon in a frying pan on medium high heat until browned on one side. After 5 minutes, turn the bacon and top with the sliced tomatoes and egg (if desired). Continue cooking for a few minutes, and when egg is nearly done to your liking, top with grated cheese. Cover the pan, reduce heat to medium low and cook until cheese is melted.
With a spatula, transfer the bacon, tomato, egg and cheese (which should easily come off the pan in one piece) to the middle of a sliced bap. Tuck in!