For the dough
Put the flour, melted butter, water, salt and apple vinegar in the bowl of a stand mixer. Turn on the stand mixer and knead everything until you get a soft and homogeneous dough, which will take approx. 10 minutes. Alternatively, you can also knead everything by hand. Form a ball, wrap it with cling film and let rest at room temperature for 30 minutes.
For the filling
Melt butter in a pan and add ground oat flakes and breadcrumbs. Toast over medium heat for a few minutes, stirring frequently to avoid burning. Remove from heat and set aside to cool. In the meantime, wash and pit the Val Venosta cherries and put them in a bowl. Add sugar, vanilla sugar, ground hazelnuts, starch, cinnamon and salt. Stir and set aside until the dough has finished resting.
Preheat the oven to 190 degrees (convection oven) after the resting time of the dough. Lightly flour a clean cloth and roll out the dough on it with a rolling pin. Stretch it gently with your hands to make it very thin. It hardly breaks as it is very elastic. Brush with melted butter. Spread the mixture of breadcrumbs and oat flakes over the entire surface and make sure you leave approx. 2-3 cm along the edges. Then also distribute the Val Venosta cherry filling over the entire surface. Roll up. Close the ends of the dough and press well to make them stick and to avoid spilling the filling. Transfer to a baking sheet lined with baking paper. Brush with the remaining melted butter and bake for approx. 35 minutes. Remove from the oven, sprinkle with powdered sugar and serve hot or cold. You can serve it with a scoop of ice cream or whipped cream to make it even more delicious.