Preheat your oven to 350°F (175°C). Grease and flour a baking pan.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy. Add the eggs, sour cream, and vanilla extract, mixing well.
In another bowl, whisk together the flour, baking soda, and salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined. Fold in the mashed bananas.
Pour the batter into the prepared baking pan and bake for 45 minutes or until a toothpick comes out clean.
While the cake is baking, prepare the cream cheese frosting by beating the softened butter and cream cheese together. Add the vanilla extract, powdered sugar, and heavy whipping cream, mixing until smooth.
Once the cake has cooled, spread the cream cheese frosting over the top.
Notes
You can add chopped nuts or chocolate chips to the batter for extra flavor.