Preheat the oven to 350 degrees F (180 degrees C).
Add the All-Purpose Flour (170 gram), Granulated Sugar (150 gram), Banana (2), Sunflower Oil (80 milliliter), Baking Powder (1/2 teaspoon), Baking Soda (1/2 teaspoon), Salt (to taste), Sour Cream (4 tablespoon), and Egg (1) to a large mixing bowl.
Beat on a medium speed with a handheld mixer until well combined.
Pour mixture into a buttered baking dish, and spread into an even layer.
Bake for 25 minutes, or until a knife or toothpick inserted into the middle comes out clean.
Prepare the icing by mixing the Powdered Confectioners Sugar (100 gram), Cream Cheese (100 gram), and Ground Cinnamon (1/2 teaspoon) together with a handheld mixer over medium speed.
Spread the icing over the cake once it is fully cooled.
Cut into bars, and serve.