Pat dry turkey breast with paper towels.
Season with salt and pepper, slipping salt under skin where possible.
Combine butter, minced garlic, sage, rosemary, thyme, paprika, and parsley.
Let it rest in the fridge until ready to use. You can make the herb spice a day or so in advance if desired.
Loosen up the turkey skin by carefully running your fingers between the skin and the meat; the skin is very fragile so be careful not to tear it up.
Generously rub the turkey with the herb butter combination and seasoning under the skin of the turkey breast. Let it rest in the fridge for up to 24 hours.
Remove turkey from the fridge an hour before cooking; this will bring it to room temperature.
Position the rack in the lowest part of the oven, remove any other racks.
Preheat your oven to 400ºF (200ºC).
Place onion, celery, and garlic in a 3-qt. baking dish, then place the turkey breast-side up.
Roast the turkey for 30 minutes, then reduce the heat to 325°F. Continue to roast until an instant-read thermometer registers 165°F in the thickest part of the breast; about 1 hour or more depending on the size of your turkey breast.
If the turkey is browning too fast, cover the breast, tent with a piece of foil to prevent over-browning.
Remove turkey from the oven and let it sit for about 15- 20 minutes before carving so the juices settle back into the meat. Reserve turkey drippings to make gravy here. Discard the herbs and onions. Serve it with this gravy.