Preheat oven to 325 degrees F. Rinse turkey; pat dry with paper towels. If desired, season body cavity with salt. Pull neck skin to back and fasten with a small skewer.
If a band of skin crosses the tail, tuck the ends of the drumsticks under the band. If there is no band of skin, tie the drumsticks securely to the tail with 100-percent-cotton string. Twist wing tips under the back.
Place turkey, breast side up, on a rack in a shallow roasting pan. Insert an oven-going meat thermometer into the center of one of the inside thigh muscles. (The thermometer should not touch bone.) Brush turkey with oil. Cover turkey loosely with foil.
Roast turkey for 1-1/4 hours. Toss onion wedges and unpeeled garlic cloves with the 2 tablespoons oil. Spoon the onion mixture around the turkey and roast about 1-1/4 hours more or until the thermometer registers 160 degrees F.
Remove foil; cut band of skin or string between drumsticks so thighs cook evenly. Carefully spread the Sweet Onion Jam over turkey. Continue roasting, uncovered, for 30 to 45 minutes more or until thermometer registers 180 degrees F.
Transfer turkey, onion wedges, and garlic to a serving platter. Cover turkey with foil and let stand for 15 minutes.
Meanwhile, for gravy, pour pan drippings into a large measuring cup; skim fat from drippings. Strain the remaining pan drippings and add chicken broth, if necessary, to equal 1-3/4 cups. In a medium saucepan combine wine and flour; stir in strained pan drippings. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 1 minute more. Carve turkey; serve with gravy. Makes 12-14 servings.
Sweet Onion Jam
Cut off about 1/4 inch of the pointed top of whole garlic bulb so that the individual cloves show. Place the bulb, cut end up, in a custard cup. Drizzle with olive oil. Cover with foil and bake in a 325 degree F oven for 45 to 60 minutes or until the garlic cloves feel soft when pressed. Cool. Gently squeeze out the garlic paste from the individual cloves into a saucepan. Stir in sweet onion, Granny Smith apple, balsamic vinegar, and sugar. Bring to boiling over medium-high heat, stirring occasionally; reduce heat. Simmer, uncovered, about 30 minutes, stirring occasionally, until the onion and apple soften, turn transparent, and the mixture thickens. Cool. Transfer to a covered container and chill for up to 1 day. Makes about 1 cup.