Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla and mashed banana.
In a separate bowl, sift together the flour, baking soda and salt. In a measuring cup, combine the buttermilk and oil. Add the flour mixture and buttermilk mixture alternately to the creamed mixture, stirring just until blended.
Divide batter evenly between the prepared pans. Bake for 25 to 30 minutes in the preheated oven, or until a toothpick inserted into the center of the cake comes out clean.
Allow cakes to cool in pans for 10 minutes, then turn out onto a wire rack and cool completely.
For the frosting, combine the cream and confectioners' sugar in a medium bowl and beat until smooth. Spread frosting over the top of the cooled cakes.
Interesting Facts
Bananas are a great source of potassium, vitamin B6, and dietary fiber.
Bananas are also high in antioxidants, which help protect cells from damage.
Buttercream frosting is a classic topping for cupcakes, but can also be used to decorate cakes and other treats.