Preheat the oven to 250˚F.
In a bowl, combine the ingredients for the dry rub: paprika, 2 tablespoons of brown sugar, salt, cumin, cinnamon, black pepper and red pepper flakes.
Dry the ribs with paper towels, peel the thin membrane that covers the bone side and discard it. Cut the rack into 2 pieces.
Place the ribs in an aluminum foil covered baking sheet.
Season the ribs on both sides, with the dry rub. Be as generous as you can on the meat side.
Cover the ribs with aluminum foil and seal them.
Bake for 1½ hour until the meat thermometer marks 155˚F-160˚F.
In the meantime, in a small pot over medium heat, add the oil and sauté the onion, scallion and garlic, until wilted, about 5 minutes.
Add the tomato paste, vinegar, Worcestershire sauce, the rest of the sugar, mustard, water and rum, stir and bring to boil.
Once it boils, reduce the heat and simmer for 10 minutes. Reserve.
Preheat a charcoal grill.
Place the cooked ribs on the grill, over indirect fire and brush them both sides, with abundant rum and mustard BBQ sauce.
Grill covered for 5 minutes.