Prep the Ribs: Start by removing the thin, silver membrane from the back of the ribs. This helps the seasoning penetrate the meat and makes them more tender. Use a dull knife to lift the corner and a paper towel to grip and pull it off.
Apply the Dry Rub: In a small bowl, mix the brown sugar, paprika, garlic powder, onion powder, salt, pepper, and cayenne. Pat the ribs dry with paper towels. Generously rub the spice mixture all over both sides of the racks, pressing it into the meat.
Slow Cooking: Wrap the ribs tightly in heavy-duty aluminum foil. Place them on a baking sheet or on a grill set to indirect heat at 275°F (135°C). Cook for about 3 hours until the meat is tender and has started to pull away from the bone ends.
Basting with Sauce: Carefully open the foil and drain any excess fat. Brush a thick layer of BBQ sauce over the top of the ribs. Leave the foil open or move the ribs directly onto the grill grates if using a barbecue.
Caramelizing the Glaze: Increase the heat to 400°F (200°C) or move the ribs under a broiler for 5 to 10 minutes. Watch closely as the sugar in the sauce bubbles and caramelizes into a sticky, delicious glaze. Remove and let rest for 10 minutes before slicing.