In a large skillet, brown ground beef and onion in the oil; add seasoning and tomatoes. Cover and simmer over low heat for 15 minutes. Add kidney beans. Pour meat mixture into a greased 1-quart baking dish. Top with corn bread batter, spreading carefully over meat mixture with a wet knife. Bake at 425° for 20 minutes.
Serve hamburger pie with a tossed green salad.