Mix flour and baking powder in a bowl. Add sugar, vanilla sugar, 1 pinch of salt, egg and butter and knead with the dough hook of a hand mixer first at low, then at highest speed to a smooth dough
Grease the tart mould with lift-off base (26 cm Ø) and dust with flour. Press the dough evenly into the mould and brush the surface with milk. Score the surface of the cake with a fork in a diamond shape. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 35 minutes