In a small bowl, mix brown sugar, chili powder, garlic powder, onion powder, cumin, paprika, salt and cayenne. Rub spice mixture evenly all over the ribs, including bone ends.
Instant Pot Method
Place trivet in bottom of pressure cooker insert. Add water and apple cider vinegar. Stand the racks of ribs on the trivet.
Set cooker to Pressure Cook HIGH. Set cook time to 27 minutes. Ribs are fully done when pulling away from bone and reach 180 - 195°F. Finish by grilling or broiling.
Oven Method
Preheat oven to 300°F,
Place 2 sheets of foil on rimmed baking sheet. Set ribs on top and wrap tightly. Bake for 2 hours. Open foil, brush on sauce and finish under the broiler.
Slow Cooker Method
Place ribs in slow cooker and cook *6 - 8 hours on LOW. Finish by grilling or broiling.
Finishing by Grilling or Broiling
Brush ribs with favorite sauce if desired.
TO GRILL - cook over HOT grill 3 - 5 minutes until pork is browned or sauce is caramelized.
TO BROIL - preheat broiler to HIGH. Place ribs on rimmed baking sheet, bone side down. Broil 1 - 2 minutes until browned or sauce is caramelized.