How to make
Separate the egg whites from the yolks. Beat the egg whites into a foamy mixture.
Mix the yolks with the sugar and citric acid and beat them into a fluffy mixture.
Add the cocoa, ground walnuts, vanilla and baking powder and stir everything. Gradually, add the whipped egg whites in small portions and stir.
Pour the mixture into a baking pan lined with greased baking paper and bake the sponge cake layer at 390°F (200 degrees) for 20 minutes.
Leave the sponge cake layer to cool down before using it.
The Gluten-Free Sponge Cake Layer is ready.