Preheat oven to 170 deg C. Line a 8 inch square tray all sides up. Sift cake flour, baking powder, baking soda and cinnamon powder into a bowl for later use.

Peel apples, cored and chopped to pieces.

In a large bowl, combine melted butter, sugar, egg and vanilla extract together with a hand whisk.

Drop in chopped apples and walnuts and fold with a rubber spatula. Fold the flour mixture into the wet mixture until just blended.

Spread evenly into the lined cake tray. Bake for about 30 minutes in the preheated oven, or until a skewer inserted in the center comes out clean.

Leave cake to cool, slice and dust with some icing icing sugar before serving.