Preheat the oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or two 9-inch round pans.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In a large mixing bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the eggs one at a time, then stir in vanilla extract.
Mix in the mashed bananas and sour cream until smooth.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Do not overmix.
Pour the batter into the prepared pan and spread evenly.
Bake for 30–35 minutes (for a 9x13 pan) or 25–30 minutes (for round pans), until a toothpick inserted in the center comes out clean.
Allow the cake to cool completely before frosting or serving.
Prep Time: 15 minutes | Cook Time: 35 minutes | Total Time: 50 minutes
Kcal: Approx. 280 per slice (without frosting) | Servings: 12