Remove the thin membrane from the back of the ribs for maximum tenderness.
In a small bowl, mix brown sugar, paprika, black pepper, salt, garlic powder, onion powder, and cayenne pepper.
Rub the seasoning mixture evenly over both sides of the ribs.
Cut each rack in half to fit into the crockpot.
Place the ribs into the crockpot standing up with the meat side facing out.
Pour barbecue sauce over the ribs, coating them generously.
Cover and cook on low for 7–8 hours or on high for 3–4 hours until tender.
For caramelized sauce, place ribs on a baking sheet, brush with more BBQ sauce, and broil for 5 minutes.