How to Make It
In a large stockpot or plastic tub, mix 1 1/2 gallons of water with the salt and sugar; stir to dissolve the salt and sugar. Add the turkey to the brine, breast side down and refrigerate for 10 to 12 hours.
Remove the turkey from the brine, rinse it in cold water and pat dry with paper towels. Discard the brine.
Preheat the oven to 400°. Place half of the onions, carrot and celery in the turkey cavity. Using kitchen string, tie the turkey legs together, then bring the string around the turkey and tie the wings at the breast. Scatter the remaining onions, carrot and celery in a large roasting pan. Oil a V-shaped rack and set it in the pan. Transfer the turkey to the rack, breast side up. Brush the turkey with the melted butter. Pour 1 cup of water into the pan and roast the turkey for 45 minutes.
Baste the turkey with the pan juices and add 1 more cup of water to the pan. Roast the turkey for about 1 hour and 45 minutes longer, basting it with the pan juices every 30 minutes or so and adding another 1/2 cup of water to the roasting pan whenever the vegetables begin to brown. (To ensure juicy breast meat, Anderson rotates the turkey a quarter turn each time she bastes it.) The turkey is done when an instant-read thermometer inserted in an inner thigh registers 170°. Transfer the turkey to a carving board, cover loosely with foil and let rest for 20 to 30 minutes before carving. Reserve the juices in the roasting pan for making the gravy.