In the bowl of the stand mixer, rub the flour, butter, sugar and almonds together until the mixture resembles breadcrumbs.
Sprinkle the mixture onto the lined baking tray and refrigerate or freeze until ready to use (i suggest to prepare the day ahead).
Butter and flour a 9.5 inches spring form pan, line the bottom with baking paper and set aside.
In a sauce pan place diced apples, butter, cinnamon, sugar and vanilla powder.
Cook for a few minutes until lightly cooked, but still firm.
Heat fan oven 325F - 160°C.
In the bowl of the stand mixer, whisk whole eggs with sugar until light and fluffy.
Pour 1/3 of the eggs/sugar mixture in another bowl: add oil, melted butter and calvados and mix to combine.
Add sifted flour with baking powder to the remaining 2/3 of the eggs mixture.
Add the previous mixture (eggs with butter, oil and calvados) and mix to combine.
Then, add the diced apples and gently mix to combine.
Pour the mixture into the prepared pan and bake for 10 minutes.
Sprinkle the almond crumble on the surface and bake for 35 minutes (i baked for a further 20 minutes……so, 65 minutes overall).
Ceck with a skewer if the cake is done.
Let cool, then dust with snow sugar.