How to cook
Heat the oven to 356°F (180 °C). Butter a rectangular baking dish.
Beat the butter with the sugar, add the eggs and continue beating.
Mash the bananas with a spoon and add them to the mixture above along with the chopped walnuts.
Sift the flour and add it to the dough. Pour it into the baking dish and bake 60-85 min., then let it cool and slice it.