How to Make It
Preheat oven to 325°F. Combine chile powder and salt in a small bowl; rub mixture over ribs. Wrap each rack in aluminum foil and place on a rimmed baking sheet. Roast until bones can be pulled out with just a bit of tension, 2 hours to 2 hours and 15 minutes.
Meanwhile, whisk together ketchup, vinegar, sugar, pepper, hot sauce, and mustard.
Preheat broiler. Unwrap ribs and baste with half the sauce. Return unwrapped ribs to oven and broil until sauce is bubbly and glazes the ribs, 6 to 8 minutes. Transfer to a cutting board; let rest for 5 minutes before slicing. Serve ribs with remaining sauce.