DIRECTIONS
Preheat oven to 275°F with rack in middle position and line a baking sheet with aluminum foil, set aside.
In a medium bowl combine brown sugar, paprika, black pepper, salt, garlic powder, cayenne pepper, and onion powder. Whisk together until well combine and set aside.
Remove the membrane from the back of the ribs and discard. Rinse the ribs under cold water and pat dry with a paper towel.
Sprinkle about half of the spice mixture over the meatier side of the ribs. Massage the rub into the ribs until evenly coated. Then turn the ribs over and repeat.
Place the ribs with the dry rub on a piece of heavy-duty aluminum foil. Make sure that the meatier side is facing up. Evenly cover the top of the ribs with sliced onions. Wrap the ribs with aluminum foil and place on the baking sheet.
Bake for 2 1/2 hours. Check the ribs to make sure they are tender. If they are not tender cook for an additional 20 minutes and check again. Repeat until ribs are fall of the bone tender.
Remove from oven, and unwrap ribs; discard aluminum foil and drippings. Then place back on the foil lined baking sheet.
Brush ribs generously with barbecue sauce. Broil or grill for 5-10 minutes until the sauce begins to bubble and caramelize.
Remove from oven and let rest for 5 minutes before serving.
