Preparation
If using pork spareribs, have the butcher remove the membrane sheath on the back of the ribs to make them easier to cut up and eat when cooked.
Preheat an oven to 325°. In a small bowl, combine the salt, cumin, and paprika. Place the racks of ribs side by side on a rimmed large baking sheet. Pour the beer over the ribs, then sprinkle them with the seasoned salt mixture. Wrap pan tightly in a few layers of foil and bake for 2 hours. Remove from oven carefully (so liquid doesn’t slosh out) and let cool for about 10 minutes before lifting off the foil (otherwise the steam may burn you).
Meanwhile, prepare an outdoor grill: if using a gas grill, preheat to medium-high. If using a charcoal grill, prepare an indirect fire (briquettes banked on one side of the kettle).
Take ribs off the baking sheet (discard liquid in pan) and brush generously with barbecue sauce on top only, then put on grill, sauce side up, and close the lid. Grill until sauce is baked on and ribs are slightly charred, about 25 minutes, without turning ribs. To serve, slice between ribs and offer additional barbecue sauce (warmed, if you like) in a bowl alongside.