Remove the turkey from the fridge one hour prior to cooking to allow it to come to room temperature.
Preheat the oven to 180°C/356°F.
Remove the neck and giblets, and save them for gravy if you wish to make giblet gravy. Remove any pin feathers that were left behind, and pat the bird dry using paper towels. Do NOT rinse the turkey.
Tuck the wings behind the bird, then season the cavity with salt and pepper and stuff with onion quarters, garlic cloves, and fresh herbs. Truss the legs using butcher twine for better presentation.
Place on a roasting rack, season with salt and pepper, and brush with melted butter from all sides. If you wish to make gravy using the drippings, add some aromatics to the bottom of the roasting pan (I add 1 onion sliced in half, garlic, and fresh herbs).
Bake in the oven for 2-4 hours depending on the size of the bird (check cooking times in the notes below).
When it browns nicely, make herb butter (mix 2 tablespoons of melted butter with 1 tablespoon of fresh herbs), brush it over the skin using a pastry brush, then put the turkey back in the oven for 30 more minutes or until it reaches the desired temperature.
To prevent excessive browning, shield the turkey breast with foil. Check the temperature of the bird using a Thermapen kitchen thermometer. When a kitchen thermometer is inserted into the thickest part of the breast reaches 68°C/155°F, and the inner thigh reaches at least 74°C/165°F, the turkey is done and must be removed from the oven immediately.
Allow the bird to rest for 30-40 minutes and up to 1 hour before carving, this will help redistribute the juices and keep the turkey moist.
For an unstuffed bird, it should roughly take about 15 minutes per 450g/pound. Here's a rough breakdown, but remember, it is just a rough guide and you should keep checking the temperature of the meat to know when it's done.
6 pound - 2.75kg: 1 hour and 30 minutes.
8 pound - 3.6kg: 2 hours.
10 pound - 9kg: 2 hours and 30 minutes
12 pound - 5.5kg: 3 hours.
14 pound - 6.3kg: 3 hours and 30 minutes.
16 pound - 7.25kg: 4 hours
Nutrition values are calculated based on an 8lb turkey for 12 portions. These are just rough estimates.