Place a mesh strainer over a bowl and place a few pieces of Banana in the strainer. Using a spatula, push and mash the Banana through the strainer. Continue with the other 2 Bananas.
In a stand mixer, place 1/2 cup Butter and 1 1/2 cup Sugar and cream together on low using the paddle attachment. Mix together until lighter in color and creamy.
Add 2 well beaten Eggs and 1 cup of the strained Banana. Mix until well incorporated for a few seconds.
Dissolve the 1 tsp Baking Soda into the 4 Tbl Buttermmilk. Add to the mixture
Sift the 1 3/4 cups All Purpose Flour, 1 tsp Baking Powder, and 1/8 ts Salt together. With the mixer on LOW add the Flour mixture in 3 parts. Mix until fully incorporated. Use a spatula to scrape down sides and mix any streaks of Flour that remain.
Add 1 cup Chopped Walnuts and fold into the mixture.
Grease an 8 x 8 Cake Pan with Baking Pam or butter. Pour the Cake mixture into the Pan and even out the top with a spatula.