Preheat oven to 175C. Grease your pie dish.
Squeeze lemon juice on apples, and gently toss, ensuring that slices are evenly coated with the juice.
Whisk together flour, almond flour, salt, crushed cardamom, and baking powder.
In a separate bowl, whisk eggs with buttermilk and vanilla essence. With an electric mixer on medium, beat in the butter and coconut sugar until fluffy, 3 to 5 minutes.
Add in the dry mixture in 3 batches, alternating with wet mixture; beat until combined.
Transfer batter to pie dish and smooth the top (an offset spatula works well here).
Arrange apple slices on top in a slightly overlapping circular pattern.
Bake for 45-50 minutes, or until a cake tester inserted into centre comes out clean.
Adorn with flaked almonds and icing sugar. Serve and enjoy with crème fraiche or sour cream.