Cajun seasoning to tasteor your other favorite seasoning blend
2stalks celery - cut in half
Rinse your turkey, and pat dry inside & out. If you want to brine your bird and/or inject it, go ahead and do those steps first.
Preheat your oven to 275 degrees.
Combine the softened butter, chopped parsley, minced garlic, seasoning salt, onion powder, & black pepper in a small bowl. (I like using my hands for this!). Place a spatula or your hand in between the skin on the breast & the meat. Coat under the skin with the herb butter. Using your hands, spread the rest of the herb butter on top of the turkey's skin & inside the cavity as well. Sprinkle with Cajun seasoning (or seasoning of your choice)
Tie the turkey legs together with cooking twine - or use the extra skin to hold the legs together (like in the pictures in the post). Stuff the inside of the cavity with the onion quarters & celery halves. Tent a piece of tinfoil on top of the breasts area. Roast the turkey in a roasting pan on a roasting rack.
Cook at 275 for about 10 minutes per pound. A 20 pound bird would need about 3.5 hours while a 15 pound bird would need about 2.5 hours. After that time, baste the bird really well with the pan juices. Bump the heat up to 350, remove the foil, and return the turkey to the oven until the meat thermometer reaches 165 degrees - basting every 20 minutes.
Let the turkey rest for at least 30 minutes before carving. I let mine rest for 45-60 minutes myself.