Rinse turkey with cold water; pat dry. Sprinkle outside of turkey and cavity with salt and 1 teaspoon pepper; stuff cavity with apple, half of onion, and 6 rosemary sprigs. Loosen skin from turkey breast without detaching it; insert remaining 2 rosemary sprigs and sage beneath skin. Place turkey on a rack in a roasting pan.
Stir together 1 cup apple juice concentrate and butter. Attach needle to marinade injector, and fill with apple juice concentrate mixture according to directions. Inject marinade into turkey breast several times.
Bake at 350º for 1 1/2 hours; cover and bake 1 more hour or until meat thermometer registers 175º.
Remove turkey from pan, reserving 1/2 cup drippings. Cool. Remove onion, apple, and rosemary from cavity, and discard; wrap turkey in plastic wrap, them aluminum foil. Chill 8 hours.
Bring 2 cups water, remaining apple juice concentrate, and remaining half of onion to a boil in a saucepan; boil 15 minutes. Pour through a wire-mesh strainer into a measuring cup, discarding solids.
Heat reserved drippings in a heavy saucepan over medium heat; whisk in flour until smooth. Cook, whisking constantly, 1 minute. Gradually add apple juice mixture, whisking constantly. Cook, whisking constantly, until thickened. Stir in remaining 1/2 teaspoon pepper. Chill 8 hours.
Serve warm with turkey and whole-berry cranberry sauce, if desired.
NOTE: Turkey may be basted with apple juice concentrate mixture every 30 minutes if marinade injector isn't available.