Beat butter, icing sugar and egg yolk until creamy and smooth.
Add in sifted flour and milk powder. Mix until well blended into a dough. Refrigerate for 30 minutes.
Roll out pastry dough between two sheets of plastic to fit the base and sides of a 1920cm fluted tart tin. Remove scraps of pastry from the edge. Press the sides of the pastry to make it even and prick the base with a fork (this is to ensure that the base is flat after baking).
Bake pastry blind in a preheated oven at 180°C for 510 minutes.
To make the filling, whisk together lemon juice, sugar, cream and lemon rind. Beat in eggs one at a time until well combined.
Pour the filling into the pastry case and bake at 180°C for 2025 minutes or until set.
Remove tart onto a wire rack to cool completely. Serve the tart immediately.
(Chef's note: If you wish to do so, you can make the tarts in small 89cm fluted tart tins.)