In the bowl of a stand mixer, fitted with paddle attachment, knead sugar with butter,salt, vanilla and lemon zest.
Add lightly beaten eggs and mix to combine.
Add flour and knead just the time to get a smooth dough.
Roll the pastry out 4 mm thick and refrigerate for almost 4 hours.
With shortcrust pastry line a 7.5 inches (in diameter) perforated pastry ring and 1.4 inches in high (19 cmx3.5 cm).
With leftovers pastry, prepare lattice top and refrigerate.
In a mixing bowl, combine ricotta cheese with sugar and refrigerate for almost 2 hours.
Then, sift the mixture, add lightly beaten eggs and egg yolk and mix to combine.
In a sauce pan, cook wheat berries, milk, sugar and lemon peel for about 7/8 minutes, stirring constantly, until you get a creamy mixture.
Let completely cool and remove lemon peel.
Heat milk with vanilla and salt.
In a small bowl, combine egg yolks with sugar and flour.
Pour hot milk over egg mixture and cook, stirring constantly over medium heat, until it starts to thicken - this should take about 1 - 2 minutes.
Pour the custard into a bowl and immediately cover the surface with plastic wrap.
Let completely chill.
In a mixing bowl, combine pastry cream with ricotta cheese filling and cooked wheat filling.
Add orange blossom, candied citron and orange, cover with plastic wrap, then refrigerate for 2 hours.
Heat oven at 320F - 160°C.
Fill the pastry base with the mixture and bake for 70 minutes.
Raise the temperature at 355F - 180°C and bake for further 20 minutes.
Let completely cool before removing the pastry ring.
Dust with icing sugar to serve.