Preheat the oven to 350 ]F. Spray an 8-inch round (or 8x8-inch) cake pan with cooking spray.
Prepare the topping:
Melt the 4 T. butter in a small saucepan over medium-low heat. Stir until the butter begins to brown, 5 to 6 minutes. Remove from heat and pour the browned butter into the round cake pan, swirling it around to coat the bottom of the pan.
In a small bowl, stir together (next 3 ingredients) the topping sugars and cinnamon. Sprinkle evenly over the browned butter in the pan. Place the (1) banana slices evenly apart on top of the sugars in the pan.
Prepare the cake:
In a medium bowl, use an electric mixer to combine the butter and sugar. Beat in the other bananas, sour cream, egg and vanilla.
In a separate bowl, whisk together the flour, baking powder, baking soda, cinnamon, ginger and salt. Stir the dry ingredients into the banana mixture. Spoon the batter into the pan, spreading evenly over the bananas.
Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Remove the cake from the oven, run a thin knife along the side of the pan to loosen.
Place a serving plate on top of the pan and gently flip it over. The cake should come out of the pan and onto the plate easily. Tap the bottom of the pan if the cake needs coaxing.
Drizzle any remaining juices in the pan over the top of the cake. Serve immediately.
Notes
Tips: Use bananas that are ripe and soft with many brown spots- not the dead black variety. Turn this cake into an Upside Down Brown Butter Banana- Blueberry Coffee Cake. Instead of placing banana slices on the bottom of the pan, sprinkle blueberries on there instead. OR, Add almond slices or toasted walnuts to the topping.
Preparation time: 25 minute(s)