Rinse chicken and pat dry.
Skewer neck skin to back.
Tie drumsticks to tail.
Twist wing tips under back.
Place chicken on rack in shallow roasting pan, breast side up.
For topping: In small mixing bowl stir together yogurt, mustard and tarragon.
Brush topping evenly onto chicken.
Insert meat thermometer into center of a thigh.
Bake in 375°F convection oven on rack #2 offset for 60 to 70 minutes (or bake in 375°F radiant bake oven 1 1 /4 to 1 1/2 hours) or until thermometer registers 180° to 185°F and drumsticks move easily.
If necessary, cover chicken with foil the last 10 to 20 minutes to prevent overbrowning.
Let stand, covered, 10 minutes before carving.
Garnish with lemon leaves and lemon wedges, if desired.