Preheat the oven to 180°C. Butter and line a 18 cm loose-bottomed flan tin with baking parchment. Unroll the shortcrust pastry sheet onto the flan tin and bake for 10 minutes.

To make the filling, combine cornflour, 2 tbsp Splenda Granulated and lemon zest in a bowl and mix thoroughly. Pour the water and lemon juice into a small pan and heat gently. Combine this with the Splenda paste, and bring the entire mixture to the boil. Lower the heat and allow to simmer for 2 minutes. Mix in the egg yolks and the butter. Cook the mixture for another minute, then pour it into the flan case.

To make the topping, whisk the egg whites until they stiffen. Add the remaining Splenda, keep whisking, and then spread the mixture over the filling. Put into the oven and bake of 15 minutes.