Follow these simple steps to create your Banana Upside Down Cake:

1. Preheat the Oven: Start by preheating your oven to 350°F (175°C). Coat a 9-inch round cake pan with cooking spray or butter.

2. Prepare the Topping: In a medium saucepan, melt the butter over medium heat. Stir in the brown sugar and cook until the mixture is bubbly and combined. Pour this mixture into the prepared cake pan.

3. Arrange Bananas: Place the sliced bananas on top of the caramel mixture in the cake pan, spreading them evenly.

4. Mix Dry Ingredients: In a large bowl, whisk together the flour, baking powder, baking soda, salt, and ground cinnamon (if using).

5. Combine Wet Ingredients: In another bowl, beat the granulated sugar and softened butter together until creamy. Add the eggs one at a time, mixing well after each addition. Stir in the sour cream and vanilla extract until smooth.

6. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Take care not to over-mix.

7. Pour Batter: Carefully pour the batter over the bananas in the cake pan, ensuring it covers them evenly.

8. Bake: Place the cake in the preheated oven and bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.

9. Cool: Once baked, remove the cake from the oven and let it cool in the pan for about 10-15 minutes. This allows the caramel to set slightly.

10. Invert: Carefully run a knife around the edges of the pan. Place a serving platter over the pan and gently invert it to release the cake. Let it sit for a moment before lifting the pan away.