Heat oven to 350°F. In 2-quart saucepan, heat 6 cups water to boiling. Add bell pepper halves; boil 5 minutes or until slightly softened. Drain; set aside.
Meanwhile, in 8-inch nonstick skillet, cook ground turkey and onion over medium-high heat, stirring frequently, until turkey is no longer pink; drain. Stir in taco seasoning mix, kidney beans and tomato sauce. Heat to boiling. Reduce heat to medium-low; simmer 5 minutes, stirring occasionally.
In ungreased 8-inch square (2-quart) glass baking dish, arrange pepper halves. Spoon turkey mixture evenly into each.
Bake 10 to 12 minutes or until peppers are tender. Top individual servings with sour cream, cheese and tomato.