To make pastry, process flour, icing sugar and butter until crumbly. Add egg yolk and cold water; process until ingredients come together. Knead dough on floured surface until smooth. Wrap pastry in plastic and refrigerate 30 minutes.

Grease a 24cm round loose-based fluted flan pan. Roll pastry between sheets of baking paper until large enough to line pan. Ease pastry into pan, press into base and side; trim edge. Cover; refrigerate 30 minutes.

Preheat oven to 200°C.

Place pan on oven tray. Line pastry case with baking paper and fill with dried beans or rice. Bake 15 minutes. Remove paper and beans carefully from pastry case. Bake another 10 minutes; cool pastry case, turn oven off.

Meanwhile, combine cornflour and 1 cup caster sugar in a medium saucepan; gradually stir in juice and the water until smooth. Cook, stirring, over high heat, until mixture boils and thickens. Reduce heat; simmer, stirring, 1 minute. Remove from heat. Stir in rind, butter and egg yolks. Cool 10 minutes.

Spoon the lemon filling into the cooked, cooled pastry case; spread the filling out evenly, covering the base completely and taking it to the edge of the pastry case. Use a fork to roughen the surface of the filling. Cover; refrigerate 2 hours.

Preheat oven to 220°C.

Beat egg whites in a small bowl with electric mixer until soft peaks form; gradually add remaining sugar, beating until sugar dissolves.

Spread meringue mixture onto roughened surface of filling. Bake about 2 minutes or until meringue is browned lightly.