Preheat oven to 180º C. Grease Wonderchef Pop Cake Round Pan with some butter and dust with some flour.
Core apples, cut into wedges and slice. Arrange the apple slices on the base of the cake tin in layers. Sprinkle 2 tbsps castor sugar on top and set aside.
Sift together flour, baking powder, baking soda, salt and cornstarch into a bowl and mix well.
Add remaining castor sugar, vanilla essence, condensed milk and butter and mix well.
Add apple juice and mix to a smooth batter.
Pour batter over the apple slices in the cake tin, spread and tap a little. Place the tin in the preheated oven and bake for 45-50 minutes.
Remove the tin from oven and cool down to room temperature. Place the tin upside down over a serving plate and slowly lift the tin to loosen the cake from the tin. Serve.