Let turkey rest at room temperature 1 hour. Transfer oven rack 1 level below center and preheat oven to 350 degrees near end of resting.
Remove neck and giblets from turkey and remove any pin feathers left behind. Pat outside of turkey well dry with paper towels and dry inside as well. Tuck wings under turkey. Season cavity well with salt and pepper.
In a mixing bowl stir together butter, lemon zest, thyme and rosemary. Using the back end of a wooden spoon and starting at the back end of the turkey, carefully separate the skin from the breast leaving skin intact between breasts, front area and sides. Be careful not to tear skin or butter will melt out as it bakes.
Transfer turkey to a large roasting pan with a roasting rack (if you are looking to buy one I have this one - affiliate link).
Using the end of the spoon again stuff and spread about 1/3 of the butter total into each portion and rub hands over turkey skin to smooth around.
Rub remaining 2/3 of the butter all over turkey, except underside. Season well with salt and pepper.
Stuff onion, garlic and parsley into cavity of turkey. Tie legs together with kitchen twine if you want a better presentation**.
Bake in preheated oven until thickest portion of thigh (without touching bone) registers 165 degrees on a probe thermometer or instant read thermometer, about 2 hours 20 minutes to 3 hours 30 minutes***, while tenting top of turkey with aluminum foil during baking as needed to prevent excessive browning.
Let turkey rest 30 minutes (or up to 60 minutes) then carve****.