Preheat oven to 350 degrees. For the cupcakes, in a mixing bowl with an electric mixer, mix together the butter, bananas and sugar until light and fluffy. Add the buttermilk and eggs and mix until soft. Add the remaining cupcake ingredients and mix until smooth. Fill two muffin tins with cupcake wrappers and fill each tin 3/4 of the way full. Bake for 15 minutes, or until the center bounces back once touched. Remove from the oven and let them cool while you make the glaze.
For the glaze, place the cream cheese in a microwave safe bowl and warm for 30 seconds or until soft. With an electric mixer, mix the cream cheese until smooth. Add the buttermilk and vanilla and then the powdered sugar a little at a time. Whip until smooth. Frost the cooled cupcakes and serve.