Preheat oven to 350˚F.
Grind the hazelnuts in a food processor, either coarsly or fine, depending on preference
Add flour, sugar, vanilla, and salt and pulse a few times to mix.
Cut butter in chunks and add to dry ingredients in food processor. Mix until combined. If the dough is too dry, add a bit of ice cold water.
Line a springform pan or glass baking dish with parchment paper. Alternatively, grease springform pan or glass baking dish with some oil or butter.
Add about ½ of the dough to the baking dish and gently press down evenly.
Add the fruit.
Crumble the remaining dough on top of the fruit.
Bake for 40-55 mins or until topping is golden brown.