Rub the butter and the sugar with your fingertips just until there are no large lumps of butter remaining.

Mix in the beaten egg yolks and then rub in the two flours, previously sifted with salt, vanilla seeds and lemon zest.

Try to work quickly so that it does not become greasy, bind the dough together, then press it slightly, wrap in cling film and let sit in the refrigerator for several hours or even overnight.

Heat the milk with the vanilla bean and bring it to a gentle boil, then remove it from the heat.

In a saucepan whisk the egg yolks with the sugar and the cornstarch, then pour in some milk  in a thin stream and stir immediately, as to avoid to get scrambled eggs!

Pour in all the milk and put the saucepan on low fire.

Stir constantly with a whisk until you see the first bubbles on the surface and the custard thickens.

Remove the saucepan from the heat immediately, scrape the custard into a bowl, cover it with cling film and set aside.

Preheat oven to 180°C.

Remove the short pastry from the fridge, knead it to soften it and roll it on a floured surface with a rolling pin in a 5 mm thick sheet.

Cover a baking sheet with parchment paper (approx. 20 cm x 30 cm), then line it with the short pastry.

Sprinkle the pastry with rhubarb and berries, arranging them in an even layer.

Sift the ricotta and mix it into the custard, then spread it onto the fruit, leaving a few berries popping out here and there.

Bake the tart for about 1 hour, until the edges are golden and the centre slightly jiggles when pan is tapped.

Let it cool down, cut it into bars and dust it lightly with icing sugar.