Preheat your oven to 350°F (175°C) and grease a baking pan.
In a mixing bowl, cream together the softened butter and sugar until light and fluffy. Add in the eggs, sour cream, and vanilla extract, mixing until well combined.
In another bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the mashed bananas.
Pour the batter into the prepared baking pan and bake for 40 minutes or until a toothpick inserted in the center comes out clean.
While the cake is baking, prepare the cream cheese frosting by beating together the softened butter, cream cheese, vanilla extract, and powdered sugar. Add heavy whipping cream to achieve desired consistency.
Once the cake has cooled, spread the cream cheese frosting evenly on top.
Notes
You can add nuts or chocolate chips to the cake batter for extra flavor.