Heat oven to 300°F (150°C). Remove the membrane from the back of the ribs. Mix the 2 tbsp brown sugar, 1 tbsp smoked paprika, 1 tsp garlic powder, 1 tsp onion powder, 1 tsp salt, 1/2 tsp black pepper, 1/2 tsp chili powder, and 1/4 tsp cayenne, then press the rub all over both sides of the ribs.

Wrap the rack tightly in a double layer of foil, meat-side down. Place on a rimmed baking sheet and bake at 300°F (150°C) for 2 hours.

Stir together the 3/4 cup BBQ sauce and 1 tbsp apple cider vinegar in a small bowl.

Switch the oven to broil on high. Transfer the ribs meat-side up onto the baking sheet. Brush on half the glaze and broil 6 inches from the element for 3 to 4 minutes, then brush on the remaining glaze and broil another 2 to 3 minutes until the glaze bubbles and deepens in color.

Let the rack rest for 3 minutes, slice between the bones, arrange meat-side up on a platter, and spoon any pooled glaze back over the top.