Preheat the oven at 180 degrees C or 365 F.
Prepare a 9-inch cake pan for baking-Brush the sides with oil/butter and line with parchment paper.
Mix the baking powder, flour and salt in a small bowl.
Cut the apples into one inch thin slices.Do not immerse in water
Melt the butter.
Whisk the eggs in a bowl, once they are frothy add the sugar , melted butter, vanilla extract and rum.
Whisk it together till the sugar has dissolved a bit.
Add the flour mix to the liquid mixture to make a batter.
Add all the apples in the batter. The batter will look more of apples than a cake batter but that's alright.
Pour it into the prepared pan and bake in preheated oven at 180 degrees C or 365 F for 40 minutes.
Test with a skewer or a knife,if it comes out clean the cake is cooked, if not bake for another 5 minutes.
Let it cool for 10 minutes before transferring on a wire rack.