Place pepper halves in a 9x13 inch glass baking dish or two 9-inch glass pie plates. Microwave on high for 5 to 7 minutes or until peppers are slightly tender. If using pie plates, microwave each dish separately. In medium skillet, over medium-high heat, cook ground round and onion til browned; drain off fat. Stir in taco seasoning, kidney beans, and tomato sauce; bring to a boil. Reduce heat and simmer for 5 minutes. Place pepper halves, skin-side down, in a 9x13 inch baking dish. Spoon beef mixture evenly into pepper halves; sprinkle with cheese. Bake in a 350 degree oven for 8 minutes. Top with sour cream and tomato.