Once you’ve cut all the way through, cut along the other side of the backbone, and remove the spine. Add the backbone to the neck and giblets you’re saving for gravy or broth.
Use a knife to make a shallow cut in the cartilage on the underside of the breastbone, and use your hands to firmly push the breasts flat like an open book.
Now, it’s time to salt the bird. Use your fingers to loosen the skin away from the flesh. (Be careful but forceful; the skin is fairly elastic, and shouldn’t tear unless you pierce it with sharp acrylic nails.) Rub salt directly onto the meat under the skin, as well on the outside and underside of the turkey. Loosely cover the bird with plastic wrap, and dry-brine it in the fridge for 1 to 3 days.
On Thanksgiving Day,line bottom of oven with aluminum foil. Preheat the oven to 450°F with the rack in the lower middle position. Take the brined turkey out the refrigerator. Line a baking sheet with aluminum foil and place a wire rack on top.
Take two-thirds of the herb butter and use it to spread under the skin of the breast and thigh meat. (Another method: you can just place a dollop between the skin and meat, and smush down the skin to spread the butter evenly.) Spread the remaining herb butter on the outside of the bird.
Lay the bird flat on the wire rack and tuck the wing tips under the turkey so they don’t burn. Pour ½ cup of water into the tray. This’ll keep the drippings from burning and smoking.
Place the turkey in the oven and stab an in-oven thermometer (if you have one) into the thick part of the breast. The turkey’s done when the breast meat reaches 145°-150°F, and the thigh meat is 165°F, about 80-90 minutes.
If you see that the skin is already nice and bronzed before the meat is even close to the correct temperature, don’t fret. Just place an aluminum foil bra loosely over the bird boobs before returning the turkey to the oven so they don’t burn.