Start preparing the banana sponge cake dough. To do this, combine the yolks of two eggs with one whole egg in a deep bowl. Add vanilla sugar and granulated sugar. Beat for about 5 minutes using a mixer. The mass should turn into a light, voluminous foam, and the bubbles should become small.
Turn the whites into foam. To do this, add salt to them and beat with a mixer for 4 minutes until a fluffy soft mass is formed.
Continue preparing the banana sponge cake base. Add flour and baking powder to the yolks and mix.
Combine the mixtures. To do this, carefully and gradually add the whites to the dough. The mass should be thick. Finally, add the banana and mix everything thoroughly.
Pour the dough into the pan and place it in the oven on the middle level. Bake for 40-45 minutes. After turning off, leave the sponge inside to cool down a little.