Preheat oven to 450 degrees. Core tomatoes; slice into 1/4-inch-thick slices (makes about 3 cups); set aside. Sprinkle Mozzarella and Parmesan cheeses evenly over pizza shell; top with tomato slices, slightly overlapping. Bake until cheese melts, about 8 minutes. Meanwhile, in a medium bowl, combine romaine, watercress, roasted peppers and olives; sprinkle with Italian dressing; toss to coat. Remove pizza from oven; top with romaine and watercress mixture; cut into wedges and serve immediately. Makes 4 portions. Note: To toast tortillas, place on baking sheets in a 450 degree oven until light gold, about 4 minutes. Preparation time: 10 minutes Baking time: about 11 minutes