Preheat your oven to 350°F (175°C).

Grease two 9-inch round cake pans with butter or cooking spray and dust with flour.

Mash the ripe bananas in a bowl until smooth.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and mashed bananas until well combined.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, alternating with the sour cream. Mix until just combined, then fold in the chopped walnuts.

Divide the batter evenly between the prepared cake pans and smooth the tops.

Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool in the pans for 10 before transferring to wire racks.

Once cooled, frost with cream cheese frosting.