In a small bowl, combine brown sugar, salt, onion powder, chili powder, mustard, paprika, thyme, oregano, garlic powder, black pepper, cumin and cayenne pepper.
Remove the membrane from the underside of the ribs, pulling it down the entire length. Season ribs with brown sugar mixture, rubbing in thoroughly on both sides.
Add chicken stock and apple cider vinegar to a 6-qt Instant Pot®. Place metal trivet into the pot. Place ribs upright on top of the trivet, wrapping in a circle.
Select manual setting; adjust pressure to high, and set time for 20-25 minutes. When finished cooking, quick-release pressure according to manufacturer’s directions.
Preheat oven to broil. Line a baking sheet with foil.
Place ribs, meat side up, in a single layer onto the prepared baking sheet; brush with barbecue sauce.
Place into oven and broil until barbecue sauce is caramelized and browned, about 4-6 minutes.