Preheat oven to 475°. Wash chicken thoroughly. Slice celery stalk. Sprinkle inside cavity of chicken with thyme and salt; add 1 tsp butter, sliced celery and onion. Rub outside of the chicken with the remaining butter.
2
Tuck wing tips under the back of chicken. Place chicken breast side down on rack of roasting pan.
3
Add enough water to cover the bottom of the pan. Roast for 10 minutes then reduce the heat to 375° and roast for 20 minutes longer.
4
Turn chicken breast side up. Roast until golden brown, about another 30 minutes longer.