Preheat oven to 400 degrees.
Rinse turkey, remove giblets, and neck.
remove turkey legs from the plastic holder if needed, rinse out the inside of the turkey really well on both ends, the cavity, and the neck.
Then drain the water out of the turkey.
Place the legs back into the plastic holder.
Place thawed turkey on a rack in a roasting pan, breast side down (this will ensure juicy turkey breast and not dry meat, the juices run down to the breast)
most turkeys nowadays have a plastic piece securing the legs, you bake the turkey with that in.
Alternatively, you can tie the legs together with baking string, or simply tuck them under the bird.
Pat dry with a paper towel.
Rub room temperature butter over the top of the turkey
add salt and pepper.
Place 4 cups of water into the bottom of the roasting pan
wrap in aluminum foil
Place the turkey in the oven,
Roast the turkey for one hour at 400 degrees
then turn the oven to 200° (or 250° if your oven doesn't hold a steady lower temperature) and roast 8-9 hours
otherwise, turn the temperature to 250 degrees
Roast turkey overnight for 9-10 hours
*be sure your oven holds a solid temperature at 200 for hours and does not drop below that with an additional thermometer you put in the bottom of your oven. If your oven doesn't hold at 200°- 250°F. Most people don't have their ovens on for 8+ hours at a low temperature, and I've found they don't check them, so you could roast it at 250°.
Just before you think it's done, you can turn the oven temperature to 350° to brown the skin uncovered if it's not brown yet. This usually takes 20 minutes.
LONGER is better for slow roasting, having the turkey fall off the bone is far better than undercooked tough meat.
ALLOW PLENTY OF TIME, if your turkey needs an extra hour plan ahead for that.
Turkey will stay hot for at least an hour or TWO before carving.
The temperature of the breast should be at least 165 degrees and the thigh should be at 170 degrees. (but I really prefer when the meat is closer to 180°-185°, as long as it's slow-roasted it will not be dry, the liquid in the pan will help keep it moist, and with the breast down it won't dry out.
If your oven runs cool, it will need more time to cook.
If your oven runs hot, it may be done sooner.