Start by mashing the garlic in a mortar and pestle until it turns into a paste. In a bowl, mix the garlic with sofrito, the juice of one orange, and one lime to make your marinade.
Place the rack of ribs in a large resealable bag or baking dish, then pour the marinade all over. Make sure the rack is nicely coated, then cover and let them marinate in the fridge for at least an hour (or overnight if you want maximum flavor).
When you're ready to grill, take the ribs out of the marinade and set them on a clean surface. Generously season both sides with brown sugar, adobo, and sazón, making sure to rub it into every little nook and cranny.
Place the ribs on your grill over indirect heat, meat side up. (For indirect heat, only light one side of the grill or push the coals to one side.) Close the lid and let them cook for 1 to 1½ hours.
Flip the ribs, close the lid again, and let them cook for another 1 to 1½ hours.
While the ribs cook, mix the juice of another orange and lime with oregano and cumin to make the glaze.
After cooking the ribs for 2 to 3 hours, pour that glaze over the ribs and let them cook uncovered for another 5 to 10 minutes, just until it bubbles and caramelizes.
Take them off the grill and let them rest for about 10 minutes before slicing and serving. ¡Buen provecho!