01 - Preheat the 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, approximately 3 to 4 minutes.
03 - Add the eggs one at a time, beating well after each addition. Stir 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 fold the dry ingredient mixture into the wet ingredients using a spatula, mixing until just combined. Take care not to overmix, as this can produce a dense texture.
06 - Pour the batter into the prepared cake pan and smooth the surface with a spatula. Sprinkle chopped walnuts or pecans over the top if desired.
07 - Bake on the center oven rack for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.
08 - Allow the cake to cool in the pan for 10 minutes, then carefully transfer it to 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.