Preheat your oven to 180°C (350°F).
Prepare a 9-inch cake pan by greasing it with butter and dusting it lightly with flour, then set aside.
Strain the flour, baking powder, corn starch and salt.
Combine powdered sugar and softened butter in a separate bowl until creamy.
Add eggs and mix, then pour the milk and combine.
Add the vanilla extract and the strained dry ingredients from earlier, then mix evenly.
Transfer your German apple cake batter to the prepared cake pan.
Peel, cut into halves, and core the apples. Then, make incisions on the curved side (careful not to slice them entirely).
Arrange the apples on top of the batter, keeping even space in between.
Place your cake pan in the lower part of the oven for 40 to 45 minutes or until it turns golden brown.
Remove from the oven and let cool.
Sprinkle with powdered sugar --- enjoy!