Prepare the Ribs:

Preheat your oven to 275°F (135°C).
Remove the membrane from the back of the ribs by sliding a knife under it and pulling it away.
In a bowl, mix together brown sugar, paprika, garlic powder, onion powder, salt, black pepper, and cayenne pepper.
Rub this spice mixture all over the ribs, coating both sides evenly.

Bake the Ribs:

Wrap the ribs tightly in aluminum foil and place them on a baking sheet.
Bake in the preheated oven for about 2-2.5 hours, or until the meat is tender and pulls away from the bone.

Grill the Ribs:

Preheat your grill to medium-high heat.
Remove the ribs from the foil and brush them generously with barbecue sauce on both sides.
Grill the ribs for 5-10 minutes per side, applying more sauce as needed, until they are caramelized and charred.

Serve:

Let the ribs rest for a few minutes before slicing between the bones.
Serve with extra barbecue sauce on the side.