Line the bottom of a springform pan (26 cm Ø) with parchment paper.
Making the pastry dough:
Add all the pastry dough ingredients to the mixing bowl and coarsely combine for 15 sec / Speed 5. Scrape down the sides of the bowl with a spatula, then knead for 2 min / Kneading Mode. Note: The dough will still look a little crumbly after kneading—that's totally normal due to the volume of dough!
Transfer the dough to your work surface and knead gently by hand until it comes together into a smooth ball.
Divide the dough in half. Flatten one half into a disc, wrap in plastic wrap, and chill in the fridge.
Take 2/3 of the remaining dough half, place it into the springform pan, and press it firmly into an even bottom layer.
Roll the remaining 1/3 into two long dough ropes, place them around the inner edge of the pan, and press with your fingers to form a rim about 3 cm high.
Prick the bottom crust several times with a fork and pop the pan into the fridge as well. Now on to the apple filling!
Making the filling:
Peel, core, and dice the apples. Add them to the roughly cleaned mixing bowl along with the lemon juice, granulated sugar, and vanilla sugar.
Whisk the water and vanilla pudding powder together until smooth, then add it to the bowl as well.
Now simmer for 7 min / 100°C / Reverse / Speed 1. Note: Cooking time depends on your apples! It's a good idea to peek inside occasionally so the apples don't get too soft and turn into applesauce. On the flip side, if your apples are extra firm, extend the cooking time by 1–2 minutes.
Assembly & Baking:
Preheat your oven to 190 °C top/bottom heat.
Remove the remaining chilled dough disc from the fridge, knead it briefly by hand to soften, and roll it out on a silicone mat (or a lightly floured work surface).
Place a 26 cm plate or the bottom of another springform pan onto the rolled-out dough and trace around the edge with a knife to cut out your top crust.
Pro Tip: Don't have a matching plate or second springform base? You can do this step right at the beginning using your pan base, then pop the cut pastry disc in the fridge until you need it!
Take the prepared springform pan out of the fridge and pour in the warm apple filling. Trim any excess side crust with a butter knife so it sits flush with the apple filling.
Invert the pastry lid over the cake using the silicone mat (or carefully lift and lay it on top if you're not using a mat). Press the edges firmly to seal, then prick the top crust a few times with a fork.
Bake the covered apple cake on the lower rack of the oven for 40 minutes.
Remove from the oven and let it cool slightly.
For the glaze, whisk the powdered sugar with a tiny splash of water—just adding enough liquid to get a thick, pourable consistency.
Pour the glaze over the cake, smooth it out, and let it drip naturally down the sides in spots.
Let the cake cool completely before slicing so the filling sets nicely—overnight is ideal!
Notes
Keep it covered in the fridge, and it'll stay fresh for several days!
Feel free to fold some rum-soaked raisins into the apple filling—just skip the booze if you're serving little ones.
Swap out the vanilla for cinnamon if you love that warm spice vibe, or stick with vanilla if cinnamon isn't your thing.
Don't waste those pastry scraps after trimming the top crust! Cut out a few fun shapes and bake them into delicious shortbread cookies. :-)