Fry the onion in the butter till almost tender.
Add the hamburger, salt and pepper; stir well.
Heat mixture thoroughly but do not brown hamburger.
Spread 3 cups cabbage in a greased casserole; cover with meat mixture.
Place rest of cabbage on top.
Pour the undiluted can of soup over all.
Bake covered at 350ºF about 1 hour.
Serve with hot cooked rice.
Serves 2-3.