Add the mashed bananas, sugar, and softened butter to a mixing bowl, then beat until the mixture is creamy.
Crack the eggs into the mixture and stir until everything is well combined.
In another bowl, combine the flour, baking powder, baking soda, and salt. Mix these dry ingredients together.
Pour the dry ingredients into the wet mixture and stir until you no longer see any flour.
If desired, gently fold in the chopped walnuts to add a bit of texture.
Pour the finished batter into the bread pan of your Wolfgang Puck bread maker.
Select the "Cake" setting on the machine. Choose the "Dark" color for baking.