Preheat your oven to 250 degrees F. Line a rimmed baking sheet with aluminum foil.
Combine the garlic powder, onion powder, paprika, salt, pepper, brown sugar and cayenne pepper together in a small bowl. Set aside.
Remove the membrane from the back side of the ribs - Insert a butter knife under the membrane at one end of the ribs and lift. Using a paper towel, grip the membrane and gently pull to completely remove.
Rub the spice mixture as evenly as possible over the ribs.
Place ribs on prepared baking sheet (meat side up). Cover and seal with aluminum foil.
Bake for 3 hours, or until tender.
Remove ribs from oven and carefully remove aluminum foil. Drain and discard any juices. Brush ribs on both sides evenly with barbecue sauce.
Turn oven broiler on high and place under broiler for 3 to 5 minutes, until sauce starts to bubble and caramelize (watching carefully so that ribs do not burn).