Remove the membrane from the back of the ribs (the silvery-white sheet on the bone side). This ensures more tender ribs. Simply slide a knife under the membrane, grip with a paper towel, and pull it off.

In a small bowl, combine garlic powder, onion powder, paprika, salt, black pepper, and cayenne pepper (if using). Rub this seasoning mixture all over both sides of the ribs, pressing gently to help it adhere.

Pour water or apple juice into the bottom of your slow cooker. Cut the rack of ribs into sections if needed to fit properly. Place the ribs in the slow cooker, standing them along the sides with the meaty side facing the wall of the cooker, if possible.

Cover and cook on Low for 7-8 hours or on High for 3-4 hours. The ribs are done when the meat is tender and starting to pull away from the bones.

Preheat your oven's broiler. Line a baking sheet with aluminum foil. Carefully transfer the cooked ribs to the prepared baking sheet, meat side up. Brush half of the barbecue sauce over the ribs.

Broil the sauced ribs for 3-4 minutes, until the sauce begins to caramelize and bubble. Keep a close eye on them to prevent burning.

Remove from the broiler, brush with remaining sauce, and let rest for 5 minutes before serving. This allows the juices to redistribute throughout the meat.