Place the soft butter into a mixing bowl with the sugar. Mix and whisk the butter-sugar into a creamy consistency.
Add the Eggs to the mix and blend smooth.
Now add in the Salt and baking powder. Besides that throw in some of the flour. Start to blend the mixture and continue to add in the flour, step by step, until you have used up everything.
Mix the whole content to a smooth batter.
Peel your apples, cut into slices.
Heat up your oven to 180 Celsius/ 350 Fahrenheit.
Prepare a springform with a layer of baking paper at the bottom.
Pour the batter into the mold and spread evenly.
Arrange your apple slices on top.
Sprinkle the cinnamon and brown sugar over the apple slices.
Bake the cake for about 38 minutes or until the cake is golden on the outside and baked on the inside. Test if it's done by going into the cake with a knife. If the knife comes back clean, it's baked through.
Use sour apples if you want a cake that is less sweet.
You may leave the apple skin on the apples and just cut them into slices.
One serving size equals 1 cake slice. The nutritional details are according to one serving.