French Onion Soup - Beef Au Gratin Recipe

Ingredients

• 1/2 c butter
• 4 c thinly sliced onions
• 1 lb sirloin cubes
• 3 T flour
• 1 t cumin
• 1 T dark brown sugar
• 1 t salt
• 1/2 t pepper
• 1 qt beef broth
• 1 c shredded mozzarella cheese
• 1/2 c grated parmesan cheese