Trim fat from ribs. Cut ribs into four to six serving-size pieces For a charcoal grill, arrange medum-hot coals around a drip pan. Test for medium heat above pan. Place ribs, bone sides down, on the grill rack over drip pan. (Or, place ribs in a rib rack; place on grill rack.) Cover and grill for 1-1/2 to 1-3/4 hours or until tender. (For a gas grill, preheat grill. Reduce heat to medium. Adjust for indirect cooking. Place ribs in a roasting pan, place on grill rack, and grill as above.)
Meanwhile, for sauce, in a small saucepan gradually stir hot water into peanut butter (mixture will stiffen at first). Stir in lime juice, green onion, ginger, and cayenne pepper. Cook and stir over low heat until heated through. Spoon sauce over ribs. Makes 4 to 6 servings.