Preheat oven to 275°F (135°C). Remove membrane from back of ribs.
Combine brown sugar, paprika, garlic powder, onion powder, black pepper, salt, and cayenne pepper in a bowl.
Rub spice mixture on both sides of ribs.
Wrap ribs in aluminum foil and bake for 2.5-3 hours.
Combine BBQ sauce and apple cider vinegar in a saucepan; simmer.
Unwrap ribs, brush with BBQ sauce.
Preheat grill to medium-high. Grill ribs for 10 minutes, basting with sauce, until caramelized.
Let ribs rest before slicing and serving.
