01 - Preheat oven to 350°F.
02 - Remove giblets from turkey cavity and pat turkey completely dry with paper towels.
03 - Mix softened butter, garlic, rosemary, thyme, parsley, and lemon zest in a bowl until well combined.
04 - Gently loosen skin over turkey breast and legs. Rub half the herb butter under skin and remaining butter over entire exterior.
05 - Season turkey cavity and exterior generously with salt and pepper.
06 - Fill cavity with quartered lemon, onion, celery chunks, and carrot pieces for added moisture and flavor.
07 - Tie legs together with kitchen twine and tuck wings underneath body.
08 - Place turkey breast-side up on rack in 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 breast loosely with foil if browning too quickly.
10 - Verify turkey is fully cooked when thermometer inserted into thickest part of thigh registers 165°F.
11 - Transfer turkey to cutting board, cover loosely with foil, and rest for 20–30 minutes before carving.
12 - Skim excess fat from pan juices. 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 to taste.