Prepare the Ribs: Preheat your oven to 275°F (135°C). Remove the membrane from the back of the ribs by sliding a knife under it and pulling it away. In a bowl, mix together brown sugar, paprika, garlic powder, onion powder, salt, black pepper, and cayenne pepper. Rub this spice mixture all over the ribs, coating both sides evenly.
Bake the Ribs: Wrap the ribs tightly in aluminum foil and place them on a baking sheet. Bake in the preheated oven for about 2-2.5 hours, or until the meat is tender and pulls away from the bone.
Grill the Ribs: Preheat your grill to medium-high heat. Remove the ribs from the foil and brush them generously with barbecue sauce on both sides. Grill the ribs for 5-10 minutes per side, applying more sauce as needed, until they are caramelized and charred.
Serve: Let the ribs rest for a few minutes before slicing between the bones. Serve with extra barbecue sauce on the side.