Turn oven on to 350°F. Spray a 9x13 baking pan with cooking spray. Set aside.
Use a large bowl and a hand mixer to cream butter and sugar until they are light and fluffy.
It will appear crumbly, but if you beat it for a few minutes it will become fluffy.
Add eggs, sour-cream, and vanilla. Blend until smooth.
Add flour, baking soda and salt. Blend on low speed until well combined
Mix in the mashed banana. Spread the batter in the baking dish.
Cook for between 25 and 35 minutes, or until a toothpick inserted into the middle comes out with moistcrumbs or none. You may need to cook the toothpick a little longer if it comes out with wet batter. The edges and the top will be lightly browned.
Before frosting, let the cake cool completely.
After the cake has cooled, you have two options: Frost it immediately and serve it or cover it with tin foil so it can sit at room temperature overnight before frosting it.
Frosting with Make-Cheese Cheese