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