*See notes for brining the turkey the day before. Remove the turkey from the fridge and rest at room temperature 1-2 hours before cooking (for even cooking) Pat the turkey dry thoroughly with paper towels and remove the neck and giblets from the inside if needed.
Preheat oven to 350°F and adjust the oven rack to the lower third position. Place a roasting rack inside the roasting pan. See notes if you don't have a roasting rack.
Place the turkey on the roasting rack then fill the cavity with the onion, celery, garlic, lemon and extra sprigs of herbs and set aside.
18-20 lb turkey, 1/2 medium yellow onion, 2 stalks celery, 6 cloves whole garlic, 1/2 lemon
Add the softened butter, herbs, salt and garlic to a medium microwave safe bowl and mash well with a fork to combine.
1 1/2 cups (3 sticks) unsalted butter, room temperature, 2 tablespoons chopped fresh sage, 2 tablespoons chopped fresh thyme, 1 tablespoon fresh chopped rosemary, 6 cloves garlic, 3 teaspoons salt
Use your fingers to gently lift the skin of the turkey to separate it from the body. Slide your hand in and do your best to separate as much of the skin as possible. Spread 1/4 of the compound butter under the skin and another 1/4 on top, doing your best to spread it out.
Melt the remaining butter in the microwave in 30 second increments. Cut a large piece of cheese cloth into a 3 1/2 ft by 1 1/2 ft. Place the cheesecloth in the melted butter and push it down to submerge it fully and coat each inch of it in butter. Turn it until it soaks up all of the remaining butter.
Fold the large piece of cheesecloth in half width wise to create a double layer of cheesecloth. Drape it over the prepared bird to cover it fully.
Roast in the preheated oven for 3 1/2 - 4 1/2 hours. Adjust roasting time based on the size of your bird. See notes for roasting times per pound. Rotate the pan and baste the turkey with the drippings if desired every hour. The cheesecloth will be very dark, this is what you want.
Begin testing for doneness about 30 minutes before the total roasting time is complete, at about 3 hours. Insert an instant-read thermometer into the thickest part of the turkey. The internal temperature of the breast should read 157°F and the thigh should read 175 when it's ready to be pulled out of the oven. Don't wait until the turkey breast reads 165 or it will be overcooked. The internal temp will continue to rise as it rests.
When it's done, transfer turkey from the oven then carefully discard cheesecloth and transfer the turkey to a large serving platter or cutting board for carving. Tent it with follow and allow it to rest for 30 minutes before carving. This is the perfect time to make the gravy with the pan drippings!