For quick banana cake, cream butter, sugar and vanilla sugar in food processor until fluffy. Add the eggs one by one.
Peel bananas, mash with a fork and mix into the mixture together with the hazelnuts. Sift flour and baking powder, mix well and also gently add.
Pour the batter into a greased cake pan and bake the banana cake at 170 °C for approx. one hour (test with a stick).