Cut the pastry into a circle to line a pie dish. Blind bake at 180℃ for about 20 minutes.
Mix the egg yolks and condensed milk together, stir in the lemon juice. Pour into the pastry case and bake for 15 minutes.
Meanwhile, whisk the egg whites and cream of tartar until stiff. Add the corn flour and whisk. Add the sugar 1/3 at a time and whisk well after each addition. Spoon onto filling. Reduce the temperature to 150℃ and bake for another 10 minutes.