Preheat the smoker to 325°F. In a medium-sized bowl, use a spoon to combine the butter, salt, garlic powder, onion powder, paprika, chile powder, brown sugar, and pepper; set aside.
Place the turkey in a large baking dish with deep sides. Make sure to remove the gizzards and neck inside the turkey. Trim off any excess skin. Using your hands, gently separate the skin from the turkey. Start at the neck by the breasts, working your way down all the way to the thighs and legs.
Take the seasoned butter reserving about a third of it and place it under the skin. You will need to work this down and around the legs and thighs and all over the breast meat. Smear the rest of the butter on the skin.
Stuff the cavity with the lemon, onion, garlic, parsley, bay leaves, and rosemary. Place the turkey into the smoker in the baking dish. Smoke for about 15 minutes per pound until the internal temperature taken at the thickest part of the thigh reaches 160-165°F.
Let the turkey rest for at least 30 minutes before slicing and serving.
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Notes
This will depend on how large the bird is, but a good rule to follow is about 15 minutes per pound when cooking it at 325°F.