Preheat oven to 350 degrees F. and grease a 9x13 baking dish.
In a large bowl, mix the all-purpose flour, cinnamon, salt, and baking soda. Set it aside.
Mix the mashed bananas, granulated sugar, brown sugar, and vanilla extract until well combined.
Add the melted butter and eggs and mix well.
Add the flour mixture to the egg mixture alternating with the buttermilk. Don't overmix! Mix until well combined.
Pour the cake batter into the prepared baking dish and place it in the oven. Immediately reduce the heat to 275 degrees F and bake for 60 minutes. Don't overbake.
Once the 60 minutes are up, remove the cake from the oven and let it cool completely.
To make the cream cheese frosting, mix the cream cheese, unsalted butter, and vanilla extract until smooth. Add the powdered sugar and mix on high for 3-4 minutes or until the cream cheese frosting is nice and fluffy.
Frost the cake with the frosting and decorate with banana slices and ground cinnamon, if desried. Enjoy!
Let the cake cool completely before frosting. Bake the cake in a buttered 9x13 baking dish for best results.