01 - Remove the membrane from the bone side of the ribs to enhance tenderness.
02 - In a small bowl, mix brown sugar, paprika, smoked paprika, garlic powder, onion powder, black pepper, salt, and cayenne until fully blended.
03 - Thoroughly coat both sides of the ribs with the prepared spice rub and let rest at room temperature for 20 minutes.
04 - Heat a charcoal or gas grill to medium indirect heat (285°F to 320°F).
05 - Wrap each rack tightly in aluminum foil, adding a splash of apple cider vinegar to each packet before sealing.
06 - Place foil-wrapped racks on the grill, cover, and cook for 1 1/2 hours, turning occasionally.
07 - Unwrap ribs carefully and generously brush with barbecue sauce.
08 - Return the ribs, unwrapped, to direct medium heat on the grill. Grill 10–15 minutes, turning and applying extra sauce until caramelized and lightly charred.
09 - Allow ribs to rest for 5 minutes before slicing between the bones and serving.