For the crust: In a stand mixer, add the flour, sugar, pinch of salt and lemon zest. Mix together for about 30 seconds.
With a sharp knife, open the vanilla bean, remove the seeds and add them to the other ingredients in the mixer.
With the mixer on a medium speed, add the cold butter and mix until it looks like coarse crumbs.
In a small bowl, beat together the yolks and grappa and add it to the mixture. Keep the machine running on medium speed. The dough will come together (it only takes a few seconds) and as soon as it starts leaving the sides of the bowl, turn off the machine, and by hand on a flat surface, work into shape of a disk. Cover with plastic wrap and refrigerate for about an hour.
Preheat the oven to 425 degrees F. Butter an 11-inch tart pan very well.
On a floured surface, roll out the dough to about 1/4-inch thick, and then gently lay it into the tart pan. Press the dough lightly into the round edges, then, using your fingers, press on the edges of the pan, cutting off the excess.
With a fork, poke the dough several times, all the way through to the pan. The tart will try to "rise" in the oven, so poking the tart helps it breathe in the hot air.
Bake in the oven until golden and crisp, about 20 minutes. Set aside on a cooling rack for about 30 minutes.
For the filling: Use a hand mixer to whip together the mascarpone, cream, grappa, sugar, and vanilla seeds in a large bowl. Whip until you have soft peaks.
Spread the filling on top of the cooled crust. Add the berries by just dropping them on the cream, there is no need to push the fruit. If the cream is light and fluffy they will slowly drop into the filling. Top with shaved dark chocolate.