1. Preheat your oven to 275°F (135°C).
2. In a small bowl, combine the brown sugar, paprika, black pepper, salt, chili powder, garlic powder, onion powder, and cayenne pepper.
3. Remove the thin membrane from the back of the ribs. This step is optional but helps the seasoning penetrate better.
4. Generously rub the spice mixture all over both sides of the ribs.
5. Wrap each rack of ribs in aluminum foil and place them on a baking sheet.
6. Bake the ribs in the preheated oven for 2.5 to 3 hours, or until they are tender and the meat is pulling away from the bone.
7. Remove the ribs from the oven and carefully remove the foil.
8. Preheat your grill to medium-high heat.
9. Brush the ribs with barbecue sauce and place them on the grill.