Remove the silver skin membrane from the bone side of each rack: slide a butter knife under the membrane near one end, grip it firmly with a paper towel, and pull it off in one steady motion. Pat both racks completely dry with paper towels.

In a small bowl, combine smoked paprika, brown sugar, kosher salt, garlic powder, onion powder, black pepper, cumin, cayenne, and mustard powder. Mix thoroughly.

Coat both sides of each rack generously with the dry rub, pressing it firmly into the meat. For best results, cover and refrigerate for at least 2 hours or up to 24 hours before grilling.

Combine ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, smoked paprika, garlic powder, onion powder, cayenne, and honey in a small saucepan over medium heat.

Stir to combine and bring to a gentle simmer. Cook for 10–12 minutes, stirring occasionally, until the sauce has thickened slightly and the flavors have melded together.

Remove from heat, stir in the butter until melted, and season with salt and pepper to taste. Set aside. The sauce can be made up to 5 days ahead and stored in the fridge.

For charcoal: Light a full chimney of charcoal and arrange the hot coals on one side of the grill only, leaving the other side completely empty. Place the grill grate on top and allow to heat for 10 minutes. Target temperature: 250–275°F on the indirect side.

For gas: Preheat all burners on high for 10 minutes, then turn off the burners on one side and reduce the active burners to low-medium to maintain 250–275°F. Oil the grill grates on the indirect side.

Place the ribs bone-side down on the indirect (cool) side of the grill. Close the lid and grill undisturbed for 2 hours, maintaining a consistent temperature of 250–275°F. Resist the urge to open the lid frequently.

After 2 hours, remove the ribs from the grill and place each rack bone-side down on a large piece of heavy-duty foil (double-layered). Drizzle 2 tablespoons of apple juice or beer over each rack, then seal the foil tightly into a packet.

Return the foil-wrapped racks to the indirect side of the grill. Close the lid and cook for another 45–60 minutes, until the meat has pulled back from the bones by about 1/4 inch and a toothpick slides through with almost no resistance.

Carefully unwrap the ribs (watch for hot steam). The ribs should be visibly tender and the bones partially exposed. Brush a generous layer of BBQ sauce over both sides of each rack.

Move the ribs to the direct (hot) side of the grill, bone-side down. Grill over direct heat for 5–7 minutes per side with the lid open, brushing on additional sauce every 2 minutes, until the glaze is deeply caramelized and slightly charred at the edges.

Remove from the grill and allow to rest for 10 minutes before slicing between the bones. Serve with remaining BBQ sauce on the side.