Wash hands. Use your hands to mix the ground beef and the 2 pkgs of taco seasoning together good. Drain corn, beans, and tomatoes. Mix this all with diced onion. Work it all in with the ground beef/taco seasoning mixture. Put into a 2 qt (8 x 11.5) baking dish. Spread plenty of ketchup on top to cover. Bake at 350 for approx 45 min.               If you prefer, use a mixture of ketchup with taco sauce on top.         I made this recipe up myself, but I think it is pretty good. Everyone seems to like it,