01 - Remove the membrane from the underside of each rack to promote tenderness.
02 - Mix the brown sugar, paprika, smoked paprika, garlic powder, onion powder, black pepper, salt, and cayenne pepper in a small bowl until thoroughly blended.
03 - Coat both sides of the ribs evenly with the spice mixture and allow them to rest at room temperature for 20 minutes.
04 - Preheat a charcoal or gas grill to medium indirect heat, approximately 285-320°F.
05 - Wrap each rack securely in aluminum foil and add a splash of apple cider vinegar to each packet.
06 - Place the foil-wrapped ribs on the grill, cover, and cook for 1 hour 30 minutes, turning the packets occasionally to ensure even cooking.
07 - Unwrap the ribs carefully and brush both sides generously with barbecue sauce.
08 - Return the unwrapped ribs to the grill over direct medium heat. Grill for 10 to 15 minutes, turning and basting occasionally, until the sauce is caramelized and slightly charred.
09 - Let the ribs rest for 5 minutes before slicing between the bones and serving.