Preheat oven to 375F.

Remove any giblets from the turkey.

Use a large spoon to carefully separate the skin from the breast of the turkey, as shown. Rub ¼ cup of butter under the turkey skin, directly on the turkey breast. Rub remaining butter all over the turkey.

Place a halved lemon and a small amount of rosemary and thyme inside the turkey cavity. Make a small cut 4" down from the turkey opening and push the turkey legs through. Alternatively, you can use kitchen string to tie the turkey legs together. Sprinkle turkey liberally with poultry seasoning.

Place water and quartered onions in the bottom of a roasting pan. Quarter the remaining lemon and add to the roasting pan. Cut the top off of one head of garlic, add it to the roasting pan, and then peel and crush each clove of the remaining garlic. Add to roasting pan, then place the turkey overtop. (You can use a roasting pan if desired.)

Bake for 3 ½ to 4 hours. Cover with the top of the roasting pan or tinfoil for the first half of the baking time.

Once you remove the cover, baste the turkey with the turkey juices every 20-30 minutes. At the 3 hour mark, pour the olive oil over the turkey in any spots that are not browning as deeply as other spots. Cook until turkey reaches an internal temperature of 165F.

Cover and let turkey rest at room temperature for 5-10 minutes before carving. (This is a great time to make gravy or finish up other side dishes.)