Put the flour, sugar and salt in a bowl and mix. Stir the egg and add the butter pieces. Knead everything into a dough using your hands. If the dough appears a little too dry, you can add 1-2 tbsp of cold water. Shape the dough into a ball, wrap in cling film and put it in the fridge for about 30 minutes.
Preheat the oven to 200 degrees. Wash, peel and quarter the apples and cut them into even slices. Place the apple pieces in a bowl, sprinkle with lemon juice and add a pinch of cinnamon.
Grease the tart form with a little butter. Roll out the dough on a floured work surface and line the form evenly with it. Press the dough lightly with your hands and spread the apple slices on top. Bake the tart for about 20 minutes.
Caramelise the sugar in a pot at medium heat. Add the apple juice and let it boil down lightly. Take the tart out of the oven and spread the apple sauce evenly over it. Bake the tart for another 5 minutes and then enjoy immediately. A ball of cinnamon ice cream goes well with this.
Notes
The recipe requires a small tart form with a diameter of approx. 16 cm.