Make sure the turkey is defrosted according to the label.
Remove giblet & liver (usually in the neck cavity) and the neck bone in the main cavity. Save these for turkey gravy later if desired.
Use a paper towel to blot dry both the outside skin and inside cavity.
Combine salt, baking powder, sugar, and ground black pepper.
Rub the above mixture all over the outside of the Turkey. Work your finger into the area underneath the skin in the neck cavity as well. Do it slow and carefully.
Once done covering the turkey in salt/pepper mixture, pour the remaining into the main cavity, shake and use your hand to make sure all the inside cavity area is rubbed well with salt.
Now chop and cut all the sweet onion, apple, and lemon into quarters, celery into 2-inch sticks, peel garlic, etc.
Stuff all the above into the turkey main cavity as well as rosemary/thyme/sage.
Use a piece of turkey tie or kitchen twine to tie turkey legs together.
Tuck the wings to the back.
Situate turkey with its breast facing up and chill in the refrigerator, uncover to brine and dry over night.