Preheat the oven to 350°F.
In a small saucepan melt the butter over medium heat. Add the lemon zest and juice and the teaspoon of thyme to the butter and stir. Set aside.
Remove the giblets from inside the turkey cavity. I also usually trim some of the excess fat around the neck of the turkey. Pat the skin dry with paper towels, this promotes browning and crisping.
First, you'll need to place the onions, celery and carrots in the bottom of a roasting rack, then place the rack on top. Place the turkey on top of the roasting rack. Tuck the wing tips under the body of the turkey, this will help stabilize the turkey when carving, plus it makes it easier to carve the breast. Tie the legs together with butcher twine.
Brush the turkey with the herb butter mixture all over and generously season with salt and pepper.
Cover the turkey with aluminum foil and transfer the roasting pan to the preheated oven. Cook covered for 2 hours.
Remove the aluminum foil and transfer the turkey back to the oven. Roast for an additional 1½ hours. Use a meat thermometer to know when the turkey is done. When the thermometer is inserted in the breast it should read 165°F, and 180°F in the thigh.
Remove the turkey from the roasting pan to a cutting board and cover with aluminum foil. Let it rest for 20 minutes before carving and serving.