1. For the shortcrust pastry, knead butter, powdered sugar, vanilla sugar, flour, baking powder, eggs, cinnamon, and salt into a dough using a hand mixer first, then finish kneading by hand.

2. Shape the dough into a flat rectangle, wrap in foil or airtight packaging, and place in the refrigerator for at least 1 hour.

3. Line a baking tray with parchment paper and dust the work surface with a bit of flour. Preheat the oven to 180°C.

4. Divide the dough in half; roll out one half larger than the baking tray, place it in the tray, and fold up the edges slightly.

5. Prick the dough with a fork several times and spread the apple sauce evenly over it.

6. Roll out the other half of the dough and place it over the apple sauce. Adjust with smaller pieces if necessary.

7. Bake the cake in the preheated oven on the middle rack for about 45 minutes. If the cake becomes too dark, reduce the temperature slightly.

8. Let the apple sauce cake cool completely on the tray.

9. Mix powdered sugar and lemon juice smoothly and spread it evenly over the cake. Allow the icing to set before cutting into pieces and serving. Tip: It pairs well with whipped cream with a hint of vanilla sugar!