MAKE THE SHORTCRUST PASTRY:
Lightly grease a deep 23cm pie dish and set aside.
Sift 1 1/2 cups of plain flour into a bowl and dice 125g of butter in, then mix with your fingertips to make a breadcrumb texture. Stir in the icing sugar.
Make a well in the centre and add 2 tablespoons of water, then mix with a large flat edge knife by making cutting actions through the mixture until it forms a beaded texture. Add 1 - 2 more tablespoons if the mixture is too dry. Do NOT knead the dough.
Gather the dough together in a ball and place between two sheets of baking paper on a flat surface. Roll out the dough between the paper until it is flat and wide enough to cover the bottom and the sides of the pie dish.
Line the pie dish with the pastry, trim and fork the edges of the pastry and cool in the fridge for 15 minutes. Preheat the oven to 180 degrees C.
Once pastry has cooled, line the pastry shell with baking paper and fill with baking beads or red kidney beans, then bake for 10-15 minutes. Remove from the oven and take out the kidney beans and baking paper. Bake the pastry shell on its own for another 10 minutes. Remove and let cool. Turn the oven up to 220 degrees C.
MAKE THE LEMON FILLING:
Put remaining 1/4 cup of plain flour, 1/4 cup of cornflour and 1 cup of caster sugar in a saucepan. Whisk in the lemon juice, lemon zest and 1 1/2 cups of water. Place over a medium heat and whisk continually until the mixture boils and thickens, then lower the heat and let it cook for 1 minute. Remove from the heat. Whisk in remaining butter and then whisk in the egg yolks slowly one by one. Cover the saucepan in gladwrap and place in the fridge to cool.
When cool, pour the lemon filling into the pastry shell and let it sit while you make the meringue topping.
MAKE THE MERINGUE TOPPING:
Put the egg whites and remaining 1 1/2 cups of caster sugar in a dry clean bowl. Beat with electric beaters on high for 10 minutes until the mixture is thick and glossy. Add 1/2 teaspoon of cornflour and beat it in quickly. Spread the meringue on top and then make peaks by using a flat knife to twirl and lift the meringue. Bake for 7 minutes until slightly browned and then let cool in the fridge for 15 minutes until set. Serve.
Make sure your instruments are dry when making the meringue because water can destroy the effect.
Don't knead the dough.