Thaw turkey in the refrigerator 2 to 3 days before roasting.
Prepare a large enough bucket /container/oven roasting bag. Make sure the container fits in the refrigerator.
Place 4 cups (960ml) water in a large pot. Add kosher salt and sugar. Heat up the water stirring until salt and sugar dissolve. Turn off heat. Add another 8 cups (about 2 liters) water to the salt and sugar solution. Brine is now ready to be used.
Take neck and giblets out of the turkey. Remove any excess fat and leftover pinfeathers. Wash the turkey inside out. Place turkey and brine in /container/oven roasting bag. Add some ice cubes so that the water is nice and cold. Place in the refrigerator for 8 to 16 hours turning once.
Preheat oven to 350°F (180°C). Remove turkey from brine. Rinse inside out with cold water. Discard brine.
Sprinkle turkey cavity with salt, pepper, sage, rosemary, and thyme. Stuff with lemon and onion.
Pat dry with paper towels. Tie the legs together if turkey does not come with the plastic ties for cooking. Tie a string around the turkey body holding down the wings and turn the neck skin flap over to close the top cavity. Place turkey breast side up on a roasting rack inside a deep pan.
Combine butter, pepper, sage, rosemary, thyme, and lemon zest in a small dish. Microwave for 30 seconds on 70% power. Rub mixture all over turkey. Sprinkle all over with a little salt and pepper.
Place a moisten wad of clean kitchen paper towels on the turkey.
Roast for about 3 hours, basting and replacing the dried out kitchen towels with a fresh moisten towels every 30 to 45 minutes during roasting. Remove the paper towels the last 30 minutes of roasting so that turkey can turn brown.
According to FDA, the turkey is safe when a food thermometer inserted into the innermost part of the thigh and wing and the thickest part of the breast reaches a temperature of 165°F (74°C).
Remove from oven and allow turkey to rest for 20 minutes before carving.