Lemon-Thyme Roasted Chicken

1 lemon, cut in half
1/2 medium onion
5 lb. whole roasting chicken
1/4 C. butter or margarine, softened
3 garlic cloves, pressed or finely minced
2 tsp. chopped fresh thyme
1 tsp. coarse salt
1 tsp. coarsely ground black pepper
1 C. chicken broth
1/2 C. dry white wine
2 Tbsp. all-purpose flour
fresh thyme and roasted garlic for garnish, if desired

Place one lemon half and onion half into the chicken cavity.
Stir together butter, garlic, and thyme. Starting at the neck cavity, loosen the skin from breast and drumsticks by inserting fingers and gently pushing between skin and meat (Do not totally detach skin.) Rub half of the butter mixture evenly under the skin.
Tie ends of legs together with string; tuck wings tips under. Rub the remaining half of butter mixture over chicken. Place chicken, breast side up, on a lightly greased rack in a lightly greased shallow roasting pan. Sprinkle with salt and pepper.
Bake at 450 degrees F for 30 min. Reduce heat to 400 degrees and bake for 55-60 min. or until a meat thermometer inserted into thigh registers 180 degrees, basting occasionally with pan drippings and turning pan for even browning. Cover loosely with aluminum foil to prevent excess browning, if necessary. Remove to a serving platter, reserving drippings in pan. Cover chicken with foil and let stand 10 min. before slicing.
Add broth to reserved drippings in pan, stirring to loosen browned bits from bottom.
Whisk together pan drippings, wine, and flour in a small saucepan. Cook, stirring often, over medium heat 5 min. or until thickened. Serve with chicken. Garnish if desired.