Let the turkey stand at room temperature 1 to 2 hours. Place a rack in the bottom third of the oven; preheat to 425 degrees .
Under the skin: Carefully slide your fingers between the skin and the breast meat. Spread the butter evenly under the skin, onto the breast meat and the tops of the thighs. Tuck the wings behind the turkey. Place it, breast side up, on a rack in a large roasting pan.
In the cavity: Season the cavity with salt and pepper, then stuff with the celery and onion. Using kitchen string, loosely tie the legs together. Season the turkey all over with salt and pepper.
Pour the broth into the roasting pan. Roast the turkey for 1 hour. Rotate the pan, reduce the oven temperature to 375 degrees and continue roasting until an instant-read thermometer inserted in the thickest part of the thigh (dont touch the bone) registers 155 degrees , 1 1/2 to 2 hours. (The temperature will rise about 10 degrees as the turkey rests.)
On the roasted bird: Transfer the turkey to a serving platter. (Reserve the roasting pan and pan drippings for gravy.) Brush the EVOO all over the turkey; season. Tent the turkey with foil and let stand at least 20 minutes before carving.