Step 1: Prepare the Ribs: Remove the thin membrane from the bony side of each rack of ribs. Use a paper towel for grip to pull it off. Pat the ribs dry with paper towels.
Step 2: Make the Dry Rub: In a small bowl, combine brown sugar, smoked paprika, garlic powder, onion powder, salt, black pepper, chili powder, cumin, and cayenne pepper (if using). Mix well.
Step 3: Apply the Rub: Generously coat both sides of the ribs with the dry rub, pressing it into the meat.
Step 4: Preheat Oven: Preheat your oven to 275°F (135°C).
Step 5: Wrap the Ribs: Place each rack of ribs, meat-side up, on a large piece of heavy-duty aluminum foil. Pour 2 tablespoons of apple cider vinegar over each rack. Tightly wrap the ribs in the foil, ensuring no steam can escape. Double-wrap if your foil is thin.
Step 6: Slow Bake: Place the wrapped ribs on a baking sheet and bake for 3 hours and 15 minutes to 3 hours 45 minutes, or until incredibly tender. The meat should easily pull away from the bone.
Step 7: Prepare for Glazing: Carefully remove the ribs from the oven. Increase oven temperature to 400°F (200°C) or preheat your broiler. Unwrap the foil, discarding the liquid, and place the ribs directly on the baking sheet, meat-side up.
Step 8: Apply BBQ Sauce: Generously brush the top of the ribs with about 1 cup of your favorite BBQ sauce.
Step 9: Glaze and Caramelize: Bake for 15-20 minutes at 400°F, or broil for 5-10 minutes, watching carefully to prevent burning, until the sauce is bubbly, sticky, and slightly caramelized.
Step 10: Rest and Serve: Let the ribs rest for 5-10 minutes before slicing and serving. Brush with remaining BBQ sauce if desired.