Preheat your oven to 200°C. Line a flat baking tray with parchment paper so the sponge does not stick. Make sure the paper covers the tray evenly. This helps the batter spread smoothly and bake evenly.

Place the whole eggs and icing sugar in a large mixing bowl. Beat the mixture using an electric mixer until it becomes pale, thick and fluffy. This step adds air to the batter and creates the sponge’s soft texture.

Sift the almond flour and plain flour into the egg mixture. Add vanilla extract and gently fold everything together using a spatula. Mix slowly so the batter stays light and airy without losing the trapped air.

In another bowl, beat the egg whites with a pinch of salt until soft peaks form. Slowly add the granulated sugar while mixing. Continue beating until the egg whites become glossy and hold firm peaks.

Carefully fold the whipped egg whites into the almond batter using gentle movements. This keeps the mixture fluffy. After that, add the melted butter and fold again slowly so everything combines smoothly.

Pour the batter onto the prepared baking tray. Spread it evenly using a spatula so the sponge layer stays thin. Bake for about 10 to 12 minutes until the sponge becomes lightly golden and soft.

Remove the tray from the oven and allow the sponge to cool slightly. Lift it carefully using the parchment paper and place it on a cooling rack. This helps prevent moisture from building underneath.