01 - Preheat oven to 350°F. Grease and line a 9-inch round or square cake pan with parchment paper.
02 - In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer until light and fluffy, about 3 minutes.
03 - Add the eggs one at a time, beating well after each addition. Mix in the mashed bananas, buttermilk, vegetable oil, and vanilla extract until thoroughly combined.
04 - In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until evenly distributed.
05 - Gradually add the dry ingredient mixture to the wet ingredients, folding gently with a spatula until just combined. Be careful not to overmix.
06 - Pour the batter into the prepared cake pan and smooth the top with a spatula. Sprinkle chopped nuts evenly over the surface if desired.
07 - Bake on the center rack for 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean.
08 - Let the cake cool in the pan for 10 minutes, then carefully invert onto a wire cooling rack to cool completely.
09 - Once the cake has cooled completely, spread cream cheese frosting evenly over the top if desired. Slice and serve.