- Preheat the oven to 140 °C (fan) or 160 °C (top and bottom heat).
- For the shortbread base, mix the flour with the butter, sugar and salt in a bowl. Rub the butter into the flour with your fingers until the mixture is crumbly. Add the water until you have a dough which can easily be brought together by hand.
- Tip the dough into the lined baking tin and press it evenly into the base and sides. Bake in the oven for 30 minutes until light golden brown.
- Bake in the oven for 30 minutes until light golden brown.
- Meanwhile, mix the eggs with the cornflour, sugar, lemon juice and salt in a bowl.
- Pour this mixture onto the shortbread base and bake for another 30 minutes in the oven. The centre should still wobble slightly when you take the tart out of the oven. Allow to cool completely.
- Before serving, dust with icing sugar and serve immediately.