1. Place chicken breasts, 1 at a time, between 2 pieces of plastic wrap (or in a plastic bag). Pound each chicken breast until about 1/4 inch thick, then cut it into two slices. Season with salt and pepper. Cover the baking dish with aluminum foil. Transfer chicken to the baking dish.
2. Slice bell pepper, onion and tomatoes.
3. Preheat the oven to 350 degrees F (175 degrees C).
4. Top each chicken piece with onions, tomatoes and peppers
5. Put a thin layer of mayonnaise on top of the chicken slices. To squirt mayonnaise, use a pastry bag or a plastic sandwich bag (cut a small hole at one corner of the plastic bag so the mayonnaise can pass through).
6. Add a layer of cheese to each piece.
7. Bake for about 25 minutes.