Preheat the oven broiler.
Place an oven rack a few inches below the heating element.
Place the racks on a cutting board, bone side up, and remove the membrane (or “silver”) from the back of the ribs.
Penetrate the silver with a knife, then work your fingers underneath it until you have 2 to 3 inches cleared.
Use a kitchen towel to grab the membrane and then gently yet firmly pull the membrane all the way off the rack of ribs.
Discard the membrane.
Rub the ribs with the vinegar all over and on both sides.
Pat racks dry with paper towels or a clean kitchen towel.
Sprinkle the ribs with the rub.
Line a baking sheet with foil and set a cooling rack on top.
Lay the ribs on top of the rack in a single layer.
Make sure the meaty side of the ribs is facing up.
Broil the ribs for about 5 minutes, until the rub is bubbling and caramelizes into an even brown coating.
Remove the baking sheet of ribs from the oven.
Decrease oven temperature to 300°F.
When the temperature is lowered, return the baking sheet of ribs to the oven.
Roast for 2½ to 3 hours for spareribs or 1½ to 2 hours for baby back ribs.
Halfway through cooking, cover the ribs with aluminum foil to protect them from drying out.
About 30 minutes before the end of cooking, brush the ribs with barbecue sauce, cover with the foil again, and finish cooking.
The ribs are done when a knife slides easily into the thickest part of the rib meat.
Remove the ribs from the oven and let them rest, covered, for about 15 minutes.
Cut between the bones to separate the individual ribs.
Serve immediately with extra barbecue sauce for dipping, if you like.
