Line a half sheet pan with foil, ensuring it covers the entire surface.
Peel the silver skin away from the back of the rib rack if present, then trim off any large pieces of excess fat, leaving a good portion for flavor.
For the Spice Rub: Combine salt, black pepper, garlic powder, onion powder, cumin, smoked paprika, and cayenne pepper in a small bowl. Sprinkle half the mixture over the top of the ribs and rub to coat. Flip, sprinkle the remaining seasonings, and rub to coat. Wrap the ribs in saran wrap and refrigerate for at least 2 hours, or up to 24 hours.
Preheat the oven to 250 degrees F. Unwrap the ribs and place them directly onto the foil-lined baking sheet. Cover tightly with another piece of foil and bake for 3-1/2 hours.
Carefully remove the top piece of foil and drain any excess liquid from the pan. Brush the BBQ sauce generously over the top of the ribs, then bake for an additional 30 minutes or until the top is caramelized.
Let the ribs rest for 15 minutes before slicing and serving to retain juices.