Banana Upside Down Cake

Preheat oven to 350℉.
Make the cake batter: In a large bowl, bring together softened butter, brown sugar, sour cream, milk, egg, vanilla extract, mashed bananas, and cinnamon. Whisk to combine. Add flour, baking powder, baking soda, and salt to the mixture. Fold to combine.
Make the topping: Place the butter in the cake pan. Place in the warm oven that is pre-heating and allow the butter to completely melt (a few minutes). Once butter is melted, remove the cake pan from the oven. Mix cinnamon and brown sugar together. Evenly sprinkle the brown sugar mixture over the melted butter. Arrange the halved bananas at the bottom of the cake pan.
Pour half of the cake batter over the arranged halved bananas. Use spatula to press down on the batter to remove any air bubbles formed, especially between the bananas. Pour the rest of the cake batter into the pan and evenly spread out cake batter.
Bake at 350℉ for 40 minutes.
Remove cake from oven. Insert a toothpick to the center of the cake to check for doneness. Cake is done if the toothpick comes out clean. Allow cake to cool for at least 10 minutes.
Gently run a knife around the outside of the cake to make sure it doesn't stick to the side. Place a large plate over the cake pan. Gently flip cake over keeping the plate firmly on the cake pan.
Allow to cool for a few more minutes.
Serve and enjoy!