Beat the butter, vanilla sugar and sugar until fluffy. Add the flour, chestnut flour, vanilla pudding powder, baking powder, lemon zest, salt, mineral water and sour cream and work into a smooth dough. Place the dough in the springform cake tin. Drain the peaches and collect the juice. Slice the peaches and spread them on the cake in a fan-like pattern. Bake for approx. 45 min. at 180 °C in a fan oven. Leave the tart to cool in the springform cake tin. Prepare the cake glaze with the collected juice and rose water according to the instructions on the packaging and spread it on the peaches. Chill the tart in the fridge.