Crockpot Pizza

1 pound ground beef
1 package pepperoni, sliced
1 (15 ounce) can pizza sauce
2 cups mozzarella cheese
1/2 package rigatoni noodles
1/4 cup onion, chopped

Brown ground beef and onion, drain. Put into crockpot or casserole. Add slightly cooked rigatoni. Then add cheese and pepperoni slices. Add pizza sauce. Toss lightly. Cook until cheese is melted.