Put butter, sugar, salt and cinnamon in a mixing bowl and beat with the whisk of the electric hand mixer for about 3 minutes. Gradually add the eggs and work them in thoroughly.
Sift flour and baking powder and stir in. Mash the bananas with your hands and knead with the walnuts under the very firm cake batter. Now slowly, little by little, stir in enough milk until the dough has a soft, neither too firm nor too liquid consistency.
Pour the dough into a buttered loaf pan, smooth it out and bake in an oven preheated to 175 ° C for 45 - 55 minutes. Carefully turn the banana bread out of the mold and let it cool a little on a wire rack.