Mix cornflour and lemon juice into a smooth paste.
Whisk eggs in a pan, add butter, sugar, lemon juice, zest, and paste, then stir over medium heat until thickened.
Preheat oven to 160°C and grease the cupcake tin.
Blend flour, butter, and sugar in a food processor, then add egg yolks and water to form a ball.
Knead the pastry briefly, wrap in clingfilm, and chill for 30 minutes.
Line the cupcake tin with one quarter of the pastry and chill for 20 minutes.
Blind bake for 15 minutes, remove beans, and bake for 15 more minutes.
Roll remaining pastry, line muffin tins, and chill for 20 minutes.
Blind bake muffin cases for 12 minutes, remove beans, and bake for 3 more minutes.
Grease and line two 15cm sandwich tins.
Cream butter and sugar, beat in eggs, then stir in flour, lemon zest, and juice.
Bake cakes for 12-13 minutes until golden and springy.
Remove cakes from the oven and cool completely.
Whisk egg whites until stiff peaks form.
Boil sugar and water to 121°C, then whisk syrup slowly into egg whites until stiff.
Trim excess pastry and remove larger case from the tin.
Trim lemon cakes to fit inside the pastry cupcake base.
Layer sponge and lemon curd in the pastry case and top with meringue.
Fill small pastry cases with lemon curd and top with meringue.
Arrange tarts on a stand with the large cake at the top.