For the Ribs, heat oven to 350F (176C). Line a large rimmed baking sheet with aluminum foil and fit sheet with a roasting rack; set aside.
Remove the silver skin from the underside of the ribs by inserting a paring knife under silver skin and pulling it away from ribs; set aside.
Mix together brown sugar, mustard powder, paprika, cumin, salt, pepper and garlic powder in a small bowl. Rub both sides of ribs with spice mixture. Transfer to prepared sheet. Cover tightly with aluminum foil and bake until ribs are tender, about 1 hour 15 minutes.
For sauce, heat oil in a small saucepan over medium heat. Add onions and cook until soft, about 5 minutes. Add garlic and cook for an additional minute. Add bourbon, stirring until absorbed followed by apple butter, ketchup, Dijon, vinegar, Worcestershire, brown sugar, cinnamon, salt and pepper. Bring mixture to a boil and reduce heat to low. Simmer for 35 minutes, stirring occasionally.
Heat broiler to high. Broil ribs in centre of oven until slightly charred, about 10 minutes, flipping halfway. Baste and flip repeatedly until caramelized, about 15 minutes. Set ribs aside to rest for 5 to 10 minutes before slicing. Serve with remaining sauce.