Prepare the turkey brine: Fill a 20-30 quart pot with 2 gallons of water.
Remove 2 cups of water from the pot and add it to a saucepan with the kosher salt. Heat the two ingredients over medium heat and whisk until the salt has dissolved. Do not bring to a boil. Remove from heat. Add the salted water back into the pot and whisk together.
Next, add the oranges and the lemons to the salt water.
Finally, add the turkey to the pot. Make sure the turkey is completely submerged in the water.
Place the pot in the refrigerator for 12 hours or overnight.
Prepare the turkey for roasting: Preheat the oven to 325ºF and remove the turkey from the brine and let any excess liquid drain from the cavity of the turkey. Pat the turkey dry with paper towels.
Add all of the ingredients for the basting liquid into the bottom of a large basting pan and mix the ingredients together. Place the metal rack for the turkey in the basting pan and place the turkey breast side-up in the pan.
Season the outside of the turkey with the turkey seasoning and massage the seasoning into the turkey with your hands making sure to cover as much of the outside as you can. Then, place the two pads of butter under the skin of each turkey breast.
Drizzle the olive oil over the turkey and massage the oil into the skin.
Lastly, stuff the onion, garlic, thyme, oregano, and rosemary into the cavity of the turkey.
Roast the turkey: Place the turkey into the oven and roast it for 3-3.5 hours (about 13 minutes per pound) or until the internal temperature reaches 165ºF in the thickest part of the turkey. Make sure to baste the turkey every hour, on the hour. If the skin begins to brown too much in the last hour, place tin foil over the top of the turkey.
Remove the turkey from the oven when the internal temperature reaches 165ºF. Then, let the turkey rest for 20 minutes before carving.
Serve the turkey with gravy and other sides.