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 buttermilk salad 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 and chill.
To serve, arrange tomatoes atop lettuce leaves on individual plates. Fill the tomatoes with corn mixture. Makes 6 servings.