In a large skillet, cook beef over medium heat until no longer pink; drain. Stir in the corn, tomato sauce, water, green pepper and taco seasoning. Spoon into a greased 2-qt. baking dish., Prepare cornbread mix according to package directions for cornbread. Stir in half of the onions. Spread over beef mixture. Bake, uncovered, at 400° for 20 minutes. , Sprinkle with cheese and remaining onions. Bake until cheese is melted and a toothpick inserted into cornbread layer comes out clean, 3-5 minutes longer.