Remove the neck and giblets from the turkey's cavity and pat it dry with paper towels. Season inside generously with kosher salt and black pepper.

In a bowl, mix the butter, lemon zest, thyme, and rosemary. Separate the skin from the turkey breast and apply one-third of the butter mixture underneath the skin. Rub remaining butter all over the outside.

Stuff the cavity with quartered onion, smashed garlic, and chopped parsley, packing without overstuffing.

Preheat oven to 350°F (175°C). Roast the turkey for 2 hours and 20 minutes to 3 hours and 30 minutes. Check doneness with a meat thermometer.

Once done, remove from oven and let the turkey rest for 30 to 60 minutes before carving.