Line pie shell with foil; fill with pie weights or dried beans. Bake in bottom third of 400 degrees F (200 degrees C) oven for 15 minutes.
Remove weights and foil. Prick shell all over; bake for 10 minutes longer or until evenly golden. Let cool on rack. Filling: Meanwhile, in heavy saucepan, mix together sugar, cornstarch and salt; stir in water.
Bring to boil over medium-high heat, stirring constantly.
Reduce heat to medium-low; simmer for 3 minutes, stirring constantly. Remove from heat. Whisk one-quarter into egg yolks; whisk back into pan.
Cook over medium heat, stirring, for 2 minutes. Remove from heat. Stir in lemon rind, lemon juice and butter. Set aside. Meringue: In bowl, beat egg whites with cream of tartar until soft peaks form.
Beat in sugar, 1 tbsp (15 mL) at a time, until stiff glossy peaks form. Pour filling into cooled crust, smoothing top. Starting at edge using spatula, spread meringue around outside of hot filling, sealing to crust, to prevent shrinkage.
Spread over remaining filling, making attractive peaks with back of spoon or mounding and smoothing meringue to peak in centre. Bake in centre of 400 degrees F (200 degrees C) oven for 5 to 6 minutes or until golden.
Let cool on rack for about 5 hours or until set. Tip:
Lining the pastry with foil and weighing it down (called "baking blind") prevents it from bubbling and, especially, from shrinking. Pie weights, pellet-shaped or round, are available in kitchenware shops.
If you don't have pie weights, any kind of dried bean can be used, and reused for years. Just don't try cooking them up in a recipe afterwards.