For the pie: Whisk together half the granulated sugar, the cornstarch and the
salt. Add the water, grated peel and juice, and whisk until smooth. In a saucepan,
bring the mixture to the boil over moderate heat, stirring constantly until it begins
to thicken. Remove from the heat.
With an electric mixer, beat together the remaining 1/2 cup granulated sugar
and the egg yolks until light in color. Beat in 1/2 cup of the hot sugar juice mixture,
and add all of the yolk mixture to the contents of the saucepan. Stir over moderate
heat until thick. Take care that the mixture does not boil. Remove from heat, stir
in the butter, and pour the filling into the pie shell. Let cool.
Heat the oven to 350 degrees F.
Meanwhile, make the meringue topping. Beat the egg whites and the teaspoon of
juice to soft peaks. Gradually beat in the superfine sugar, beating until stiff
peaks form and all the sugar has dissolved. (test with your fingers). Spread the
meringue over the filling, touching the edge of the pie shell. This will prevent
Bake for 12 to 15 minutes, until the meringue is golden brown. Cool thoroughly