Preheat the oven: Set your oven to 350°F (175°C) to ensure it’s hot and ready for baking. Grease a 9x13 inch baking dish with butter or non-stick spray to prevent the cake from sticking.
Cream the butter and sugar: In a large mixing bowl, beat 1/2 cup of softened butter and 1½ cups of granulated sugar together using an electric mixer on medium speed until the mixture becomes light and fluffy, about 3-4 minutes.
Add wet ingredients: Add 2 large eggs, 1 cup of sour cream, and 1 tsp of vanilla extract to the butter and sugar mixture. Continue mixing until everything is well combined.
Incorporate dry ingredients: In a separate bowl, whisk together 2 cups of all-purpose flour, 1 tsp of baking soda, and ¼ tsp of salt. Gradually add the dry mixture to the wet mixture, stirring gently until just combined.
Mix in the bananas: Fold in 1 cup of mashed bananas gently. You want to maintain a bit of texture, so don’t overmix.
Pour and bake: Pour the batter into the prepared baking dish and spread it evenly with a spatula. Bake in the preheated oven for 25-35 minutes or until a toothpick inserted into the center comes out clean.
Cool the cake: Once baked, remove from the oven and let it cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.
Prepare the frosting: In another bowl, beat 1/2 cup of softened butter and 1 bar (8 oz) of cream cheese until smooth and creamy. Add 1 tsp of vanilla extract, then gradually mix in 3 cups of powdered sugar. Finally, add 2 tbsp of heavy cream to achieve a smooth and spreadable consistency.
Frost the cake: Once the cake is completely cool, spread the cream cheese frosting evenly over the top using a spatula. Slice into squares and serve!