1 1/2 lbs. ground beef
1/4 c. chopped onion
1/2 c. catsup
6 oz. tomato paste
1 tsp. oregano
1 1/2 tbsp. brown sugar
2 tbsp. vinegar
3/4 tsp. mustard
Salt
Mozzarella cheese, shredded
Parmesan cheese

Brown and drain meat and onion. Add rest of ingredients and heat through. Spoon on halved hamburger buns. Top with cheeses. Broil until brown.