Place an oven rack in the center of the oven and preheat it to 300°F. Trim the ribs, removing excess fat. Trim the thicker end to even out the thickness. (Cook the trimmed meat with the ribs as a cook's bonus.) Turn the ribs over and remove the silvery membrane from the back of the ribs.
Line a sheet pan that's at least 2 inches deep with heavy-duty aluminum foil and place a wire cooling rack in it. If you do not have a cooling rack, crumple a long sheet of aluminum and roll it into a rack-sized donut that is at least 2 inches thick. Place the trimmed ribs on the rack. Pat off any excess moisture with a paper towel.
Make a rub by mixing salt, pepper, garlic powder, onion powder, smoked paprika, brown sugar, cayenne, ground mustard, and melted butter.
Rub the seasoning generously all over the meaty top of the ribs in a thick layer.
Pour chicken broth into the sheet pan, being careful not to pour it on the ribs. Place the sheet pan in the oven. Lower the temperature to 250°F. Bake uncovered for 30 minutes.
Cover the ribs in aluminum foil and bake for 60 minutes, rotating the sheet pan midway through.
Remove the aluminum foil and brush the ribs with 1 cup of bbq sauce. Bake for an additional 30 minutes or until tender. Every rack is different. The ribs are ready when a fork can easily pull the meat off the bone.
Turn the heat in the oven on broil. Brush the ribs with an additional 1/2 cup of bbq sauce and place under the broiler for a few minutes, just until a little char develops. Remove the ribs from the oven and rest for 15 minutes. Cut the ribs to your desired size, serve, and try not to lick your fingers!