1 (12-to 14-pounds) turkey at room temperature 1 hour, neck and giblets (excluding liver) reserved for turkey stock
1 apple, cut into chunks
1 small onion, quartered
1 small bunch thyme
1 cup water
For cider glaze:
1 cup unfiltered apple cider
2 tablespoons sugar
1/2 tablespoon stick unsalted butter, cut into chunks
2 cups dry white wine
Melted unsalted butter if necessary
1/3 cup all-purpose flour
About 4 cups turkey or chicken stock
Preheat oven to 425°F with rack in lower third. Rinse turkey inside and out and pat dry. Put turkey on rack in roasting pan and season inside and out with 2 teaspoons salt and 1 teaspoon pepper. Put apple, onion, and thyme in large cavity. Fold neck skin under body, then tuck wing tips under breast and tie drumsticks together with string.
Roast turkey and Make cider glaze:
Add water to pan and roast, without basting, 1 hour. Meanwhile, boil cider and sugar in a small heavy saucepan, stirring until sugar has dissolved, until reduced to about 1/4 cup, 8 to 10 minutes. Remove from heat and whisk in butter 1 tablespoon at a time, whisking until emulsified. Let glaze stand until ready to use.
After turkey has roasted 1 hour, rotate pan 180 degrees. Roast, without basting, 40 minutes more.
Brush turkey all over with all of glaze and continue to roast until an instant-read thermometer inserted into fleshy part of each thigh (test both; do not touch bone) registers 165 to 170°F, 5 to 15 minutes more (total roasting time: 1 3/4 to 2 hours).
Carefully tilt turkey so juices from inside large cavity run into pan. Transfer turkey so juices from inside large cavity run into pan. Transfer turkey to a platter (reserve juices in roasting pan) and let rest, uncovered, 30 minutes (temperature of thigh meat will rise to 170 to 175 degrees F). Discard string.
Make gravy while turkey rests:
Strain pan juices through a fine-mesh sieve into 2-quart measure and skim off fat (or use a fat separator), reserving fat.
Straddle roasting pan across 2 burners, then add wine and deglaze pan by boiling over high heat, stirring and scraping up brown bits, 2 minutes. Strain through sieve into measuring cup containing pan juices.
Put 1/2 cup reserved fat (if there is less, add melted butter) in a 4-quart heavy saucepan and whisk in flour.
Cook roux over medium heat, whisking, 3 minutes. Add pan juices and stock in a fast stream, whisking constantly, then bring to a boil, whisking occasionally. Briskly simmer, whisking occasionally, until gravy is thickened, 10 to 15 minutes. Season with salt and pepper. Serve turkey with gravy.