Preheat your grill to medium heat (about 300°F).
Remove the silver skin from the back of the ribs.
Mix brown sugar, paprika, garlic powder, onion powder, black pepper, salt, and cayenne pepper in a bowl.
Rub the spice mixture generously over both sides of the ribs.
Place the ribs on the grill, bone-side down.
Cook for 2 hours, turning occasionally, and basting with BBQ sauce every 30 minutes.
Wrap the ribs in aluminum foil to keep them moist and continue cooking for another hour.
Unwrap the ribs, brush with additional BBQ sauce, and grill for 10-15 more minutes.
Remove from the grill and let rest for 10 minutes.
Slice and serve.