Mix flour, salt, sugar, baking powder and vanillin sugar in a bowl. Add egg and butter in pieces. Quickly knead to a smooth dough, divide the dough into 2 equal pieces.
Roll out the two pieces of dough on a floured work surface into 2 rectangles (each approx. 26 x 32 cm). Spread each with half of the jelly. Roll up from the short side. Wrap in foil and chill for about 2 hours.
Cut each roll of dough into approx. 1 cm thick slices. Distribute on about 3 baking trays lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) one after the other for 10-12 minutes. Let them cool down.