01 - Preheat your oven to 350°F (175°C).
02 - Remove the giblets from the turkey cavity and pat the turkey dry with paper towels.
03 - In a bowl, mix the softened butter, garlic, rosemary, thyme, parsley, and lemon zest until well combined.
04 - Gently loosen the skin over the turkey breast and legs. Rub half the herb butter under the skin, and the remaining butter all over the outside of the turkey.
05 - Season the turkey generously inside and out with salt and pepper.
06 - Fill the cavity with lemon quarters, onion quarters, celery chunks, and carrot pieces for added moisture and flavor.
07 - Tie the legs together with kitchen twine and tuck the wings under the body to ensure even cooking.
08 - Place the turkey breast-side up on a rack in a large roasting pan. Brush the skin with olive oil.
09 - Roast for 2 to 2½ hours (approximately 13-15 minutes per pound), basting with pan juices every 45 minutes. If the breast browns too quickly, tent loosely with aluminum foil.
10 - The turkey is done when a meat thermometer inserted into the thickest part of the thigh registers 165°F (74°C).
11 - Transfer the turkey to a cutting board, cover loosely with foil, and let rest for 20-30 minutes before carving to allow juices to redistribute.
12 - Skim excess fat from the pan drippings. Place the roasting pan over medium heat, add flour, and cook for 2 minutes while stirring constantly to create a roux.
13 - Gradually whisk in broth, stirring until smooth. Simmer until thickened to desired consistency. Season with salt and pepper to taste.