Prep the ribs. Remove the membrane from the back of the ribs by loosening one corner with a butter knife, grabbing it with a paper towel, and pulling it off.
Trim the ribs. Trim any loose meat, hard fat, or ragged edges so the ribs cook evenly.
Add the binder. Mix yellow mustard and apple cider vinegar together, then rub a light coat over both sides of the ribs.
Make the rub. In a bowl, mix brown sugar, smoked paprika, kosher salt, black pepper, garlic powder, onion powder, chili powder, mustard powder, and optional cayenne pepper.
Season the ribs. Coat both sides of the ribs evenly with the BBQ rub. Let them sit for 30 minutes while the smoker preheats.
Preheat the smoker. Set the smoker to 250°F using apple, cherry, pecan, hickory, or oak wood.
Start the 4-hour smoke. Place the ribs directly on the smoker grates bone-side down. Smoke unwrapped for 4 hours, letting the bark build and the color deepen.
Spritz if needed. After the first 2 hours, lightly spritz any dry edges with apple juice. Do not soak the ribs or wash off the bark.
Check the bark. Around the 4-hour mark, the ribs should have a deep reddish-brown color and the rub should be set. If the bark wipes off easily, keep smoking a little longer.
Prepare the wrap. Lay out foil or butcher paper. Add butter, brown sugar, honey, apple juice, and optional BBQ sauce.
Wrap the ribs. Place each rack meat-side down into the wrap ingredients, then wrap tightly.
Smoke wrapped for 1 hour. Return the wrapped ribs to the smoker and cook for 1 hour at 250°F.
Check tenderness. Carefully unwrap the ribs and check for tenderness. The ribs should bend easily, the meat should pull back slightly from the bones, and a probe should slide into the meat with little resistance.
Sauce if desired. If you want sauced ribs, brush a thin layer of BBQ sauce over the hot ribs after unwrapping. For a tackier glaze, place ribs back on the smoker unwrapped for 10 to 15 minutes.
Rest the ribs. Let the ribs rest for 15 to 20 minutes before slicing.
Slice and serve. Slice between the bones and serve with extra BBQ sauce, pickles, onions, cornbread, or your favorite BBQ sides.