Start with a completely thaw turkey or fresh: rinse it with water and dry it. Place the turkey with the breast up.
For the wings not to get overcooked, place them beneath the turkey. Rub the seasoning all over the turkey, until it gets reddish.
Add the salt, pepper, and poultry seasoning, inside and out (especially in the turkey’s cavity). Mix the butter with the rosemary, sage, and garlic.
Using the fingers very carefully, separate the breast’s skin from the meat, and place some spoons of seasoned butter. Bathe well the turkey and its cavity with the remainder butter.
Place the onions, the carrots, and the celery in the pan, in order to make a bed for the turkey.
Tie the legs with a cord, and place the turkey on top of the onions, carrots, and celery you already placed in the pan. Add some cups of water before placing it in the oven.
Bake at 325 °F, calculating 18 minutes per pound. Check the turkey’s temperature with a thermometer.