Barbecued Beef Cubes or Hamburger

Ingredients
1 onion, chopped
1 tablespoon butter
1 tablespoon prepared mustard
1 tablespoon Worcestershire sauce
1 tablespoon distilled white vinegar
2 tablespoons white sugar
1/2 teaspoon salt
1/2 teaspoon ground black pepper
1/2 cup ketchup
1 pound sirloin, cut into 1 inch cubes
7 ounces vermicelli pasta

Directions
In a large, heavy skillet, saute onions in butter or margarine over medium heat. Add meat, and cook until browned.

Mix in mustard, Worcestershire sauce, vinegar, salt, pepper, and ketchup. Reduce heat, cover, and simmer until sauce coats the meat. Serve hot.