Place tomatoes, stem end down, on a cutting surface. Cut each into 4 to 6 wedges, cutting to, but not through, stem end. Spread wedges apart slightly; sprinkle with salt. Cover; chill.
In a small mixing bowl, combine dressing, parsley, pepper and red pepper. In another bowl, combine corn, cheese, green pepper, cucumber and onion. Add dressing mixture; toss gently to coat. Cover; chill. Serve tomatoes filled with corn mixture over lettuce on individual plates. Makes 6 servings.