Preheat your oven to 350°F (175°C).

In a small bowl, mix together garlic powder, onion powder, paprika, 2 tablespoons brown sugar, salt, and black pepper.

Place the spareribs on a clean surface. Remove the membrane from the underside of the ribs by sliding a knife under it and pulling it off with a paper towel for better grip.

Generously rub the spice mixture all over the ribs, massaging it into the meat on both sides.

Line a baking sheet with aluminum foil and place the seasoned ribs on it. Cover tightly with another piece of foil. Bake in the preheated oven for 2 hours or until the meat is tender but not falling off the bone.

While the ribs are baking, combine ketchup, rum (if using), Worcestershire sauce, apple cider vinegar, ¼ cup brown sugar, hot sauce, and minced garlic in a saucepan. Simmer over medium-low heat for about 15 minutes, stirring occasionally until slightly thickened.

About 30 minutes before the ribs are done baking, preheat your grill to medium heat.

Remove the ribs from the oven and carefully transfer them to the preheated grill. Grill for about 15 minutes, basting frequently with the BBQ sauce and turning occasionally.

Once the ribs have a nice char and the sauce has caramelized, remove them from the grill.

Let the ribs rest for 5-10 minutes, then cut between the bones and serve with additional BBQ sauce on the side.