Peel the bananas, cut them into pieces and put them into a tall mixing bowl with lemon juice. Puree finely. Cream butter, vanilla sugar and sugar with the whisk of the hand mixer. Stir in the eggs one after the other. Mix flour and baking powder and stir into the dough alternately with the banana puree. Spread half of the dough on the greased fat pan of the oven (approx. 27 x 40 cm).
Stir the cocoa under the other half and spread it on the light-coloured dough. Using a fork, pull the dough through the dough in a spiral and bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 30 minutes (test with sticks). Remove and let cool on a cake rack. Dust with icing sugar and cut into pieces. Whipped cream tastes good with it
Waiting time approx. 1 hour. Per piece about 1930 kJ, 460 kcal. E 6 g, F 26 g, KH 49 g