If you didn’t brine your turkey, start by removing the turkey from its packaging and removing the neck, endpiece and giblets set aside the latter for making the gravy broth). Rinse the turkey thoroughly under cold water. To avoid cross-contamination, empty your sink of any objects first, and thoroughly clean the sink with soap and water afterward.
Pat turkey dry with paper towels, ensuring that it is completely dry. Moisture on the skin can prevent it from browning properly. If refrigerated, let turkey sit at room temperature for around 45 minutes to 1 hour before roasting.
Tuck the wings behind the back of the turkey. Tie the drumsticks together with kitchen twine. Some turkeys come with a plastic holder that you can use. Or, truss the turkey (see Note below).
Adjust the oven rack to the lowest position and preheat the oven to 400 degrees F. Scatter coarsely chopped onion, celery, and carrots in a roasting pan; pour 1 1/2 cups water over. Set aside.
Brush breast side of turkey with melted butter. Set turkey, breast side down, on a non-stick V- or U-shaped rack; brush back with butter. (If rack isn’t non-stick, line with foil.) Place in prepared roasting pan (with the vegetables).
Insert an oven probe or meat thermometer into the deepest part of the turkey breast, avoiding the bone. Start by inserting the probe/thermometer from the end of the breast, not the top. You want the probe/thermometer to be evenly surrounded by the meat, to the extent possible. Don’t rely on the pop-up thermometer that comes installed in some turkeys; they aren’t reliable.
Roast turkey for 1 hour, then reduce the temperature to 250 degrees and roast 1 3/4 hours longer. Add more water to the vegetables in the pan as needed.
Remove pan from oven and, using pot holders, turn the turkey over so the breast side is up. Increase oven temperature to 400 degrees, place turkey back in oven, and continue roasting until the thickest part of breast registers 160 degrees f on your probe or thermometer – about 45 minutes to 1 1/4 hours. Watch it carefully, checking the temperature after 30 minutes, if it is nicely browned and looking done.
Remove the turkey from the oven and let sit for 30 to 45 minutes on the rack in the pan, so any juices accumulate in the pan. In addition, resting the turkey allows the juices to redistribute throughout the meat, resulting in a more flavorful and moist turkey.
Remove bird and place on a large cutting board.