Preheat your oven to 325°F (165°C).
Remove the turkey giblets and pat the turkey dry with paper towels.
Rub the turkey with softened butter and olive oil, then season with salt, pepper, rosemary, and thyme.
Stuff the cavity with lemon quarters, garlic halves, and onion.
Place the turkey on a roasting rack in a large roasting pan.
Roast the turkey in the preheated oven, basting occasionally, until the internal temperature reaches 165°F (74°C) in the thickest part of the thigh.
Remove the turkey from the oven and let it rest for at least 20 minutes before carving.