Preheat oven to 375F. Season tomato slices with pepper and set aside. Place bread crumbs, cheese and Italian seasoning in a large, resealable plastic bag. Working in batches, dip the mushroom and tomato slices in egg white, and place in the bag. Shake to coat. Arrange on greased baking sheet. Spray vegetables with cooking spray. Bake 5 to 7 minutes. Turn, and coat with more cooking spray. Bake another 5 to 7 minutes or until golden and mushrooms are tender. Serve with Caesar or ranch dressing as a dipping sauce, if desired.