Apple Charlotte Roll

Peel and core the apples, slicing them thinly with a mandoline.

Line a baking sheet with parchment paper, arrange the apples, and dust with cinnamon if desired.

In a mixer bowl, beat the eggs with the sugar and vanilla extract (or vanilla sugar) until fluffy.

In a separate bowl, combine the flour, cornstarch, and baking powder, sift them, and gently fold into the egg mixture.

Pour the batter over the apples, spreading it evenly across the surface.

Preheat the oven to 180°C (350°F), place the baking sheet inside, and bake for 20 minutes.

Invert the hot sponge cake, roll it up, and let it cool covered with a towel.