Start mixing butter and icing sugar, add flour, egg yolks and the grated lemon/orange zest.
When the shortcrust pastry is even, allow it to rest in the refrigerator for one hour. Prepare the pie filling: put butter and sugar in a bowl, mix well using a whisk and add one egg at a time, then add the standard flour and finally the almond flour.
Wash the apples and cut them in half, then slice. Roll out the shortcrust pastry to half a centimetre thickness using the rolling pin, then use it to line a baking tin having a diameter of 22cm, trim the excess dough, then pour the filling. Crumble the Amaretti d’Italia and walnuts on top.
Arrange the apple slices in a spiral shape, then dust with icing sugar.
Bake in the oven at 165°C for 30/35 min.