Prepare the Turkey

1. Preheat Oven: Preheat your oven to 325°F (165°C).
2. Prep the Turkey: Remove the turkey giblets and neck from the cavity. Pat the turkey dry with paper towels.
3. Make the Sage Butter: In a bowl, mix the softened butter, chopped sage, minced garlic, salt, and pepper until well combined.
4. Butter the Turkey: Gently loosen the skin of the turkey breast and spread half of the sage butter underneath the skin. Rub the remaining butter all over the outside of the turkey.
5. Stuff the Turkey: Place the quartered onion and lemon halves inside the turkey cavity.
6. Add Broth: Pour the chicken broth into the bottom of the roasting pan to keep the turkey moist.

Roast the Turkey

1. Place in Oven: Place the turkey on a rack in the roasting pan, breast side up.
2. Roast: Roast the turkey for about 2 to 2 1/2 hours, or until the internal temperature reaches 165°F (74°C). Baste with pan juices every 30 minutes.
3. Rest the Turkey: Once done, remove the turkey from the oven and let it rest for at least 30 minutes before carving.

Make the Gravy

1. Sauté the Vegetables: In a skillet over medium heat, add olive oil and sauté the diced onion, carrots, and celery until softened, about 5-7 minutes.
2. Add Flour: Stir in the flour and cook for another minute, stirring constantly.
3. Add Turkey Drippings: Slowly whisk in the turkey drippings from the roasting pan, bringing the mixture to a simmer. Cook until thickened, about 5-10 minutes.
4. Season: Season with salt and pepper to taste.