01 - Peel away the thin membrane from the back of each rib rack using a paper towel for grip, ensuring better tenderness and spice penetration.
02 - Combine brown sugar, paprika, smoked paprika, garlic powder, onion powder, black pepper, salt, and cayenne pepper in a small bowl. Mix thoroughly until evenly blended.
03 - Generously coat both sides of each rib rack with the spice rub, pressing firmly to adhere. Allow the seasoned ribs to rest at room temperature for 20 minutes.
04 - Preheat a charcoal or gas grill to medium indirect heat, maintaining a temperature between 285°F and 320°F.
05 - Wrap each rack of ribs tightly in aluminum foil, adding a splash of apple cider vinegar inside each packet to help tenderize the meat during cooking.
06 - Place the foil-wrapped ribs on the indirect heat side of the grill, cover, and cook for 1½ hours, turning the packets occasionally for even cooking.
07 - Carefully unwrap the ribs and discard the foil. Brush generously with barbecue sauce on all sides.
08 - Return the unwrapped ribs to the grill over direct medium heat. Grill for 10 to 15 minutes, turning frequently and basting with additional barbecue sauce until the exterior is caramelized and lightly charred.
09 - Remove the ribs from the grill and let rest for 5 minutes before slicing between the bones. Serve hot with extra barbecue sauce on the side.