In a bowl, cream together butter, half the tarragon and all the lemon rind; set aside.
Wipe chicken inside and out and pat dry. Sprinkle cavity lightly with remaining tarragon and salt and pepper to taste.
Working from the neck of the chicken, gently but firmly slide hand between skin and flesh to separate, careful not to tear the skin.
Using hands, evenly spread creamed mixture in the space between the skin and the breast meat. Pull skin back in place. Truss legs and wings with string. Brush with melted buter.
Place onion, carrot and celery in bottom of roasting pan. Set chicken on top and pour in stock. Cover loosly with foil and roast in 400F oven about 1 1/4 hours or until tender; baste with pan juices every 20 minutes.
With each basting turn to another side, first breast down, then on one sider, then the other.
Finish cooking with breast up and remove foil during last 10 minutes of cooking (chicken should be well browned).
Remove from pan and let cool. Refrigerate before carving. Serve slightly chilled or at room temperature.