Homemade Banana Upside-Down Cake

Name: Homemade Banana Upside-Down Cake
Prep time: 20 min
Cook time: 35 min
Total time: 55 min
Cuisine: American
Ingredients: 0.66666668653488 cup packed brown sugar; 4.5 tablespoons unsalted butter, cut into small pieces; 3 medium bananas, sliced 1/4-inch thick; 1.75 cups all-purpose flour; 1.5 teaspoons baking powder; 1 teaspoon baking soda; 0.5 teaspoon ground cinnamon; 1 pinch salt; 0.75 cup white sugar; 0.33333334326744 cup unsalted butter, softened; 2 large eggs; 1.5 teaspoons vanilla extract; 2 medium overripe bananas, mashed; 0.33333334326744 cup sour cream