To make barbecued spare ribs in a slow cooker, place 4 pounds of spare ribs in the slow cooker along with 1 onion, 2 cups of barbecue sauce and salt and pepper to taste. Cover the cooker and cook the ribs on low for six to eight hours.
To achieve a crusty exterior, About.com recommends seasoning the ribs with salt and pepper and placing them on a rack set in a roasting pan. Broil the ribs for 20 to 25 minutes before adding them to the slow cooker.
Alternatively, make a dry rub by mixing 1/4 cup brown sugar with 2 minced cloves of garlic, 1 teaspoon salt, 1/2 teaspoon pepper and 3 tablespoons liquid smoke. Cut 4 pounds of spare ribs into serving size portions and rub them with the dry spice mixture. Layer the seasoned ribs with 1 sliced onion in a large slow cooker. Pour 1/2 cup cola over the ribs, cover the cooker and cook the ribs for eight to 10 hours on low. Drain the liquid, pour 1 1/2 cups barbecue sauce over the ribs and cook them for one additional hour.
Create a homemade sauce by combining 3/4 cup ketchup with 2 tablespoons light brown sugar and 1 tablespoon white wine vinegar. Whisk in 1 tablespoon Worcestershire sauce, 2 teaspoons paprika and 1/4 teaspoon cayenne pepper.