Cut the butter into cubes and let sit at room temperature for about 10 minutes. It will be easier to work with it that way.

Whisk baking powder and salt into the flour to distribute evenly. Rub in the butter cubes. Keep running pieces of butter between your thumbs and fingers until you get a crumbly texture.

Don’t do it for very long because this will melt the butter completely.

Add powdered sugar, lemon zest, egg yolks and sour cream. Always start with 2 tablespoons of cream, but if the dough doesn’t come together, use a bit more cream. Combine the dough in the bowl.

I always use powdered sugar. Granulated sugar takes more time to dissolve and if you knead the dough too long, it loses its flakiness.

Transfer the dough to the kitchen surface and give it a few kneads.

Divide the dough in half and form disks. Wrap them in cling film and chill for at least 1 hour.

Grease and flour the cake pan. Roll out one half of the dough. Keep pushing the edges in to create a rectangular shape so it fits snuggly in the cake pan.

Wrap the dough around the rolling pin and transfer it to the cake pan.

Prick with a fork several times so it doesn’t inflate in the oven.

For the filling, peel and grate the apples, and then weigh them. Add in sugar and simmer on low heat until apples become mushy. If the apples are too firm, add 1 tbsp of water to get them going.

Allow the apples to slightly cool and then add walnuts, rum and cinnamon.

Roll out the other half of the dough. Again, keep pushing the dough into the shape of the pan.

Wrap it around the rolling pin and gently unfold it to cover the filling.

Prick the dough with a fork again. Bake for 30 minutes at 180 °C [350 °F]. The pie should turn a light golden colour.

Let the pie cool slightly before cutting it. If you cut it straight away, you’ll break the shortcrust.

Dust with powdered sugar and enjoy! The pie will stay delicious for the next couple of days.