Preheat oven to 400°F. Coat a 15x10x1-inch baking pan with nonstick cooking spray; set aside. In a blender or food processor combine undrained diced tomatoes, tomato paste, vinegar, garlic, Italian seasoning, crushed red pepper and salt. Cover and blend or process until smooth.
In a large bowl combine the egg, 1/4 cup of the sauce, and bread crumbs. Add turkey and mix until combined. Form mixture into twelve 2-inch meatballs. Place meatballs in prepared baking pan. Bake about 15 minutes or until no longer pink (165°F).
Meanwhile, in a large skillet cook sweet pepper and onion in hot oil over medium heat about 8 minutes or until very tender, stirring occasionally. Stir in remaining sauce. Heat through. Add meatballs and stir gently to coat with sauce.
Increase oven temperature to broil. Broil split buns 4 to 5 inches from the heat for 1 minute. Line buns with cheese slices. Broil about 1 minute more or until cheese is melted and bread is toasted.
Place three meatballs in each bun. Top with sauce.
Use a hot dog bun for crumbs. Place in a food processor and pulse with several on/off turns to form crumbs.