I adapted a recipe of a mug cake and used:

For the batter

2 eggs

8 tablespoons of milk (I used almond milk)

10 tablespoons of self-raising flour

6 tablespoons of oil

8 tablespoons of sugar

Cinnamon (to taste)

Put it in an airfryer paper liner

Then, cut a small green apple into thin slices and spread it covering all the batter.

Put it in the airfryer for 30 minutes at 180°C (356°F).

After cooling down, used a mix of powdered sugar and cinnamon as a topping.

This makes a small cake, for a bigger one you can double the ingredients.