Peel the bananas and finely mash them with a fork.
Mix the spelled flour with the baking powder, vanilla sugar, spelled semolina and whole cane sugar. Mix the eggs with the butter and add the mashed bananas. Mix all ingredients together in a bowl with the mixer. Gradually add the ground walnuts. Now add the juice of half a lemon and the rum, stir again.
Grease a baking pan of your choice (square, round ) with butter and distribute the dough in the pan.