Barbecue Beef Sandwiches

Bahan-bahan (12 porsi)

• 1¼ pounds flank steak
• 1 tablespoon dark brown sugar
• ¾ teaspoon freshly ground black pepper
• 1 cup ketchup
• 1 cup chopped onion
• One 6-ounce can tomato paste
• ¼ cup packed dark brown sugar
• 3 tablespoons cider vinegar
• 2 tablespoons Worcestershire sauce
• 2 tablespoons molasses
• 1 tablespoon chili powder
• 2 teaspoons mustard
• 1 teaspoon dry mustard
• 1 teaspoon salt
• Twelve 2½-ounce sandwich buns
• red onion rings ((optional))
• dill or sweet pickle slices ((optional))