Preheat your oven to 350°F (175°C). Line a large baking sheet with heavy-duty aluminum foil for easy cleanup. If your racks are too long for your pan, cut them in half using a sharp knife between the bones. Let the ribs sit at room temperature for 30 minutes before cooking for more even results.

Turn the ribs bone-side up and locate the thin, silvery membrane covering the bones. Slide a butter knife under the membrane at one end to loosen it, then grab it with a paper towel and pull it off in one piece. This step is crucial for tender ribs.

In a small bowl, combine brown sugar, paprika, garlic powder, onion powder, black pepper, salt, and cayenne pepper. Mix thoroughly. Generously season both sides of the ribs with the dry rub, pressing it into the meat to ensure it adheres.

Place the seasoned ribs meat-side up on the prepared baking sheet. Wrap the entire pan tightly with aluminum foil, creating a sealed packet. Bake for 2 hours until the meat is tender and has pulled back from the bones by about 1/4 inch.

While the ribs bake, prepare your sauce. In a medium saucepan over medium heat, combine ketchup, apple cider vinegar, rum, molasses, Worcestershire sauce, Dijon mustard, and liquid smoke. Bring to a simmer, stirring occasionally. Reduce heat to low and simmer for 15-20 minutes until the sauce thickens.

About 30 minutes before the ribs finish baking, preheat your gas grill to medium-high heat (around 400-450°F) or prepare a charcoal grill with coals pushed to one side for indirect grilling.

Carefully remove the ribs from the oven and unwrap the foil. Transfer the ribs to the preheated grill, meat-side down. Grill for 5-7 minutes until char marks appear. Flip and generously brush with BBQ sauce. Continue grilling and basting every 3-4 minutes for a total of 20-30 minutes, flipping occasionally.

Remove the ribs from the grill and transfer to a cutting board. Tent loosely with foil and let rest for 10 minutes. Cut between the bones into individual ribs or serve as half-racks. Brush with additional warm sauce just before serving.