Brown the ground beef with the onion sliced to desired size. Cube potatoes and boil. When potatoes are done, mash and season to desire.
Drain the beef and spread evenly on the bottom of a baking dish. Add the green beans (drain all of the juice) to the top of the beef (as to layer it). Then add the tomato soup to the top of the green beans and spread it evenly over the beans (do not dilute the soup). After the potatoes have been mashed and seasoned to taste. Spread them over the tomato soup and make sure all the top is covered evenly.
Place in the oven at 350 degrees F for 20 minutes. Let stand for 5 min. and serve as a one meal skillet.