Prep Turkey: Pat dry, season cavity, stuff with lemon and onion.
Herb Butter: Mix butter, garlic, and herbs; rub under skin and over turkey.
Roast: Place on a rack, add stock, roast at 325°F (165°C) for 3–3.5 hours, basting occasionally.
Make Gravy: Skim fat, whisk in flour, and gradually add stock until thickened.
Serve: Carve turkey and drizzle with gravy.