Put the butter in a baking pan and place in the oven preheated to 220 ° C (top / bottom heat). Put the cinnamon and sugar in a small bowl and mix together. When the butter is runny, take it out of the oven.
Peel, quarter and core the apples. Then cut into thin slices and distribute evenly in the baking pan.
Mix the eggs and milk together. Then add flour and salt and stir everything again thoroughly.
Place the baking pan with apples in the oven until the butter begins to sizzle on the bottom. Take the pan out of the oven and add the batter. Then sprinkle the entire surface with cinnamon sugar.
Now bake everything for 20 minutes at 220 ° C (top / bottom heat). Serve warm.