Roll out the pastry on a floured worktop until it is 5 cm wider than a 25 cm pie dish. Line the pie dish with the pastry, leaving the excess pastry hanging over the side.
Mix together the two cheeses, the lemon juice and zest, half the sugar and five of the egg yolks.
Beat the egg whites until stiff. Add the remaining sugar and beat for another two minutes. Fold the egg white mixture into the cheese mixture.
Pour the filling into the pastry case and fold the surplus pastry edge over the filling. Lightly beat the egg yolk and brush it on the pie crust. Bake in the centre of the oven at 175°C for 30 minutes. Refrigerate for at least 2 hour.