Preheat the oven to 350 degrees.
Remove the giblets from the turkey, wash the turkey inside and out. Pllace the turkey in a large roasting pan and pat dry with paper towels.
Combine the 8 tbsp. of butter with the lemon zest, thyme leaves, minced rosemary, salt and pepper. Rub under the skin of the turkey, being careful not to break the skin. Baste the skin of the turkey with the melted butter, salt and pepper. Stuff the cavity with the bunch of thyme, bunch of rosemary, lemon, quartered onion, and garlic. You don't need to remove the skin or seeds of any of the ingredients.
Tuck the wings under the turkey, then truss the turkey by tying the wings, drumsticks and legs.
Place in the oven and roast the turkey for 2 - 2 1/2 hours, or until the juices run clear when you cut between the leg and the thigh. A thermometer should read 155 degrees. Remove the and cover with aluminum foil, let it rest for 20 minutes. Move the turkey to a cutting board, slice and serve.