Preheat oven to 425° F. Combine butter with the herb rub. Place turkey breast-side up on a rack in a roasting pan or sheet pan. Rub a generous amount of the herb and butter mixture over the entire bird, as well as underneath the skin, being careful not to tear it.
Rub the inside of the cavity with the mixture, then fill cavity with one large onion, quartered, and two stalks of celery, roughly chopped. Tie the legs together tightly with the entire length of twine supplied in kit. Tuck the wings underneath the turkey.
Place turkey in oven and roast for 20 minutes, then baste with pan juices. Lower heat to 350° F and continue to roast for approximately 15 minutes per pound of turkey. Check the temperature early and often in the thickest part of the thigh and breast. When temperature reaches 155° F, remove from oven. Let the turkey rest uncovered for up to 30 minutes, leaving you ample time to get the rest of the meal to the table. Now you can carve and serve your beautiful bird.