Preheat Oven: Set your oven to 300°F (150°C).
Prepare the Ribs: Pat the ribs dry with paper towels. In a small bowl, mix together brown sugar, smoked paprika, garlic powder, onion powder, ground mustard, cayenne pepper, salt, and black pepper. Mix in the apple cider vinegar and the soy sauce. Rub this mixture all over the ribs, ensuring they're well coated.
Arrange in Baking Dish: Place the seasoned ribs in a single layer in a baking dish or on a rimmed baking sheet lined with foil, fat side up. Cover tightly with aluminum foil.
Bake: Bake in the preheated oven for 2.5 to 3 hours, or until the ribs are tender and easily pulled apart with a fork.
Add BBQ Sauce: Remove the ribs from the oven and discard any excess liquid. Brush the ribs generously with BBQ sauce.
Broil for Finish: Set your oven to broil. Return the ribs to the oven, uncovered, and broil for 5-7 minutes, or until the BBQ sauce is bubbly and slightly caramelized. Watch closely to prevent burning.
Rest and Serve: Let the ribs rest for 5 minutes before serving. Serve with another slather of sauce or extra BBQ sauce on the side if desired.