Preheat oven (electric cooker: 150 °C/circulating air: 125 °C/gas: see manufacturer). Grease baking tin (approx. 1 1⁄4 l capacity) and dust with flour. Coarsely chop the walnuts. Melt 100 g butter. Put sugar in a large mixing bowl.
Add butter. Mix 500 g flour and baking powder, add (Frieda puts flour as a mountain directly into the mixing bowl and mix the baking powder carefully with the flour tip - this saves her washing the flour bowl).
Peel the bananas, cut them into small pieces and add them. Knead everything with your hands in the bowl. Stir in 2 tsp. cinnamon and milk with a wooden spoon. Mix in the walnuts.
Fill the dough into the mould. Bake in a hot oven for approx. 50 minutes (stick test!). Remove the cake, let it cool down for about 20 minutes, then carefully turn it out of the tin. Let it cool down and dust with icing sugar.
Tip 1: The cake is of course just as successful in a box form (11 x 25 cm; approx. 1 1⁄2 l content). Tip 2: A vegan variation works quite simply: with vegan margarine (e.g. Alsan) and soy or almond milk.