For the banana bread, melt the butter in a saucepan and remove from heat to cool. Roughly mix the flour with salt and baking powder. Either finely grind or coarsely chop the pecans or walnuts to taste.
Roughly mash two of the bananas with a fork so that they still have some consistency. Whip the other two bananas together with the sugar, cinnamon and cardamom in a blender for two to three minutes until creamy and slightly frothy.
This mixture is then blended with the melted, cooled butter, the two eggs and the vanilla extract (unless vanilla sugar is used, this can be blended directly with the remaining sugar and bananas) until smooth.
Gradually mix in the flour mixed with the salt and baking powder. Finally, on the lowest setting or by hand, mix in the nuts and the bananas mashed with a fork.
Pour the dough into a greased 26 cm loaf pan and bake at 180 degrees for about 80 minutes.