Dissolve salt in water in a container large enough to hold the turkey. Lower the turkey into the water. Refrigerate for 8 to 12 hours.
Preheat oven to 400 F. Remove the turkey from brine. Discard brine. Rinse turkey and pat dry. Slice apples and onion and cut celery into 3-inch pieces. Stuff turkey cavity with vegetables and place turkey in roasting pan. Arrange remaining vegetables around turkey and season with pepper.
Roast turkey breast side up for 30 minutes. Lower heat to 325 F and roast turkey breast side down for an additional 1½ hours. Turn again and bake until cooked through (about 25 minutes per pound). Let stand until slightly cooled before carving. Serves about 10
Use apples, cut into wedges, to brace the turkey when it is roasting breast side down.