1. Make the mop sauce: Melt the butter in a nonreactive saucepan over medium heat. Stir in the cider, bourbon, and soy sauce. Keep warm until ready to use.
2. Make the rub: Place the salt, brown sugar, paprika, pepper, mustard, garlic powder, and celery seed in a small bowl and mix with your fingers, breaking up any lumps in the brown sugar or garlic powder.
3. Prepare the ribs: Place a rack of ribs meat side down on a baking sheet. Remove the thin, papery membrane from the back of the rack by inserting a slender implement, such as a butter knife or the tip of a meat thermometer, under it. The best place to start is on one of the middle bones. Using a dishcloth, paper towel, or pliers to gain a secure grip, peel off the membrane. Repeat with the remaining rack.
4. Set aside 1 tablespoon of rub for serving. Sprinkle the remaining rub over both sides of the ribs, rubbing it onto the meat. Cover the ribs with plastic wrap and refrigerate them while you set up the grill.
5. Set up the grill for indirect grilling and preheat to medium (325° to 350°F). Place a large drip pan in the center of the grill under the grate.
6. When ready to cook, brush and oil the grill grate. Place the ribs bone side down in the center of the grate over the drip pan and away from the heat. (If your grill has limited space, stand the racks of ribs upright in a rib rack; see page 52.) If cooking on a charcoal grill, toss half of the wood chips on each mound of coals. Cover the grill and cook the ribs for 45 minutes.
7. Mop the ribs on both sides with the mop sauce. Re-cover the grill and continue cooking the ribs until well browned, cooked through, and tender enough to pull apart with your fingers, 45 minutes to 1 hour longer, 1 1/4 to 1 1/2 hours in all. When the ribs are cooked, the meat will have shrunk back from the ends of the bones by about 1/4 inch. Mop the ribs again every 15 minutes and, if using a charcoal grill, replenish the coals as needed.
8. Just before serving, brush the ribs on both sides with some of the Lemon Brown Sugar Barbecue Sauce and m ove them directly over the fire. Grill the ribs until the barbecue sauce is browned and bubbling, 1 to 3 minutes per side.
9. Transfer the ribs to a large platter or cutting board. Let the ribs rest for a few minutes, then cut the racks in half or into individual ribs. Sprinkle a little of the reserved rub over the ribs and serve at once with the remaining barbecue sauce on the side.
How to cook first-timer’s ribs in a smoker: Set up and light the smoker according to the manufacturer’s instructions and preheat it to low (225° to 250°F). Place the ribs in the smoker bone side down and smoke until cooked through, 4 to 5 hours. Start mopping the ribs with the mop sauce after 1 hour, then mop the ribs again once every hour.
Brush the ribs with the Lemon Brown Sugar Barbecue Sauce a half hour before they are done smoking. You’ll need to replenish the wood chips or chunks after the first and second hour of smoking and to replenish the coals every hour.
For barbecue sauce:
1. Combine the ketchup, brown sugar, lemon zest and juice, molasses, Worcestershire sauce, liquid smoke, mustard, onion powder, and pepper in a nonreactive saucepan and whisk to mix.
2. Gradually bring the sauce to a simmer over medium heat and let simmer until thick and flavorful, 8 to 10 minutes. Taste for seasoning, adding more lemon juice if necessary. Transfer the sauce to a bowl or clean jars and let cool to room temperature. Refrigerate the sauce, covered, until serving time; let it return to room temperature before using. The sauce can be refrigerated for several weeks.