Preheat the oven to 375F.

Sprinkle the turkey liberally with salt and pepper on the outside and inside, and rub the salt and pepper on it.

Be sure giblets are removed from inside birds cavity, and remove from plastic bag or any twine/string they have holding them in if there is any.

Put the onion, celery, carrot and lemon inside the turkey, as well as giblets and neck.

Rub butter all over turkey, including under the turkeys skin.

Put turkey inside the bag and place in a roasting pan.

Pour the chicken broth inside the turkey cavity.

Fold bag closed, and tuck under turkey so that it locks in the steam as it cooks.

Put the turkey in the middle rack of your preheated oven.

Estimate the cooking time is about 2.5 hours for the first 10 lbs, plus 12 minutes for each additional pound (for example, the cooking time for 12 lb turkey is 2.5 hours + 12 minutes + 12 minutes = 2 hours 54 minutes).

When turkey is fully cooked (insert thermometer in thickest part of bird without hitting bone to be sure) remove from oven and leave in bag for 15 minutes.

Then cut the bag open, carve, and enjoy!