1. Rub outside of pork with allspice and generous sprinkling of pepper. Let stand at room temperature 30 minutes or refrigerate up to 8 hours, allowing meat to return to room temperature before cooking.
2. Start fire in grill by placing drip pan in center and surrounding it with coals (see note) after lighting coals, place grill rack 6" above coals.
3. Place onions, one at a time, on cutting board, root end down. Using sharp knife, cut into 8 wedges, stopping two thirds of the way down to root end; do not cut all the way through. Place each onion, cut side up, in center of 12" square of foil: top with about 2 teaspoons apple jelly and 1 teaspoon margarine. Sprinkle with 1/2 teaspoon fresh thyme or 1/8 teaspoon dried and a pinch each salt and pepper. Bring foil up around onions, crimping on top but leaving 1" opening.
4. When coals are white hot, set pork roast on hot grill rack about drip pan, surround with onions. Cook, with grill covered, 1 hour 45 minutes until meat is cooked through and instant-reading meat thermometer inserted in center of roast registers 150; onions should be tender. Ten minutes before roast is done, brush with some Kentucky Bourbon sauce to glaze. Let roast stand 10 minutes before slicing. 5. Cut pork into thin slices, serve garnished, if desired, with thyme sprigs and accompanied by onions and remaining sauce. Makes 8 to 10 servings.
Note: If desired, 1 1/2 to 2 cups favorite store bought barbecue sauce, with 1/3 cup bourbon or orange juice stirred in, may be substituted, simmer at least 15 minutes after adding bourbon.
Pork loin and onions may also be cooked in oven. Heat oven to 350. Place roast, seasoned as directed and fat side up, on rack in shallow roasting pan, surround with onions. Insert oven thermometer into center of roast; roast, uncovered, about 1 hour 20 minutes. Glaze roast and serve as directed.