Place an oven rack in the lower third of your oven and preheat to 350°F.
Take the giblets and neck bone out of the turkey and drain any juices from the cavity. Trim any excess fat from the neck area, then pat the skin dry with paper towels.
Stand the turkey on the neck area, with the cavity facing up, and salt the inside of the turkey cavity with around 1 tablespoon of salt. Then, add the onion and herbs to the cavity if using. Tie the legs together with kitchen twine and tuck the wing tips under the turkey.
Place the turkey on a rack in a roasting pan with the breast side up. Brush the turkey with the melted butter and season all sides of the turkey with the poultry seasoning, pepper, and the remaining salt.
Roast the turkey for around 2½ to 3 hours until the internal temperature reaches 160°F in the deepest part of the breast.
Transfer the turkey to a cutting board. Cover with aluminum foil and let rest for 30 minutes before carving.
Notes
If the skin begins to get too dark, cover the turkey with foil.
If the drippings begin to burn, add ½ cup of water or stock to the pan.