Preheat oven to 350°. In a small bowl, combine the butter, lemon juice, lemon zest and minced thyme. Pat turkey dry. Sprinkle salt and pepper over skin of turkey and inside cavity; brush with butter mixture. Place the lemon, onion, garlic and thyme sprigs inside cavity. Tuck wings under turkey; tie drumsticks together., Place flour in oven bag and shake to coat. Place bag in a roasting pan; add turkey to bag, breast side up. Cut six 1/2-in. slits in top of bag; close bag with tie provided., Bake at 350° for 2-1/4 to 2-3/4 hours or until a thermometer reads 180°. Remove turkey to a serving platter and keep warm. Let stand for 15 minutes before carving. If desired, thicken pan drippings for gravy. Freeze option: Freeze cooled turkey and gravy in freezer containers. To use, partially thaw in refrigerator overnight. Heat through in a covered skillet, gently stirring and adding a little broth or water if necessary.