First off, melt your butter on medium heat in an oven proof skillet or saucepan.
Add the sugar and mix to evenly spread through butter.
Add the apple segments in a spiral or any way you want with the flat side in the butter.
Cook the apples in this mixture until the butter turns yellow golden. This might take a while – so when this cooks you can start with your batter.
Mix the sugar and butter until creamy – here an electric mixer is very handy.
Add the egg yolks one at a time, after each beat well.
Sift the flour, baking powder and salt and mix alternatively with the milk into the egg mixture until incorporated.
By now your apples should be done – now you can spoon the batter over your apples and spread it evenly to cover the apples.
As you put this into the oven you can start your vanilla syrup or sauce.
Bake for 30 minutes at 180 degrees C, or until your batter is golden brown – make sure your batter has a nice brown color, because you will be adding a sauce over it – it really has to be baked right through. You can test with a knife or a tester pin.
Add the milk, sugar, cinnamon and vanilla essence into a microwave safe bowl and microwave until sugar is dissolved and boiling.
Gently pour this sauce over the baked apple cake while it is still very hot.
Leave to cool for an hour or so before attempting to turn it over.
When ready, cover the cake with your serving plate and carefully (and quickly) turn the skillet over. There might still be a few pieces of apple stuck to the buttery caramel, loosen with a fork and arrange on the cake.