– 1 pound ground beef – 2 tablespoons butter – ½ cup finely chopped onion – 8 ounces tomato sauce – ½ cup ketchup – 3 tablespoons brown sugar – 1 tablespoon prepared mustard – 2 tablespoons Worcestershire  – 1 tablespoon white vinegar – ½ teaspoon salt – ¼ teaspoon pepper – ½ teaspoon garlic powder – ½ teaspoon onion powder – 1-2 tablespoons softened butter – Hamburger buns