In a large skillet, brown the ground beef and onion until the beef is cooked and onion is tender. Drain off any fat and season the beef to taste with salt, pepper, and any other spices you wish.
Stir the soup, ketchup, and mustard into the beef mixture and bring to a low simmer. Let simmer for 10 minutes or until the mixture is heated through and the liquid is reduced so the mixture is "slushy" like sloppy joes.
This is the recipe my mom always used and I hated it, now that I'm married to a beef farmer and have 3 kids I need creative recipes for ground beef. I decided to try mom's recipe one day and made one huge change, I pureed the soup first, it eliminates the huge chunks of okra and other vegetables that might turn kids off. Now my whole family loves it and it's a staple in our household