Preheat oven to 400°F. Cut off tops of bell peppers. Remove seeds and membranes. Rinse bell peppers. If necessary, cut thin slice from bottom of each pepper so they stand upright. Set aside.
Brown ground beef and onion in large skillet on medium-high heat. Drain fat. Add rice, Italian seasoning, garlic powder, salt and pepper; mix until well blended.
Pour 1 can of the tomato sauce into bottom of 9-inch square baking dish. Stuff peppers with beef mixture. Place stuffed peppers upright in baking dish. Pour remaining can tomato sauce over stuffed peppers. Cover tightly with foil.
Bake 35 to 45 minutes or until peppers are tender. Remove foil. Sprinkle stuffed peppers with cheese. Bake 5 minutes longer or until cheese is melted. Cut stuffed peppers in half. Spoon sauce in dish over each half to serve.