- 2 ½ tablespoons kosher salt
- 1 tablespoon dry mustard
- 1 tablespoon smoked paprika
- ½ teaspoon cayenne pepper
- ½ teaspoon freshly ground black pepper
- 8 pounds baby back pork ribs (8 racks)
- Low-salt chicken broth
- 1 ½ cups store-bought or homemade barbecue sauce plus more
Preheat oven to 350°F. Combine first 5 ingredients in a small bowl. Place each rack of ribs on a double layer of foil; sprinkle rub all over ribs. Wrap racks individually and divide between 2 baking sheets.
Bake ribs until very tender but not falling apart, about 2 ½ hours. Carefully unwrap ribs; pour any juices from foil into a 4-cup heatproof measuring cup; reserve juices. Re-wrap ribs in foil and set aside.
Build a medium-hot fire in a charcoal grill, or heat a gas grill to high. Add broth to rib juices, if needed, to measure 1 ½ cups. Whisk in barbecue sauce to blend.
Grill ribs, basting with barbecue sauce mixture and turning frequently, until lacquered and charred in places and heated through, 7-10 minutes. Transfer to a cutting board; cut between ribs to separate. Transfer to a platter and serve with additional barbecue sauce.