Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or line with parchment paper.
In a medium bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon. Set aside.
In a large bowl, cream together butter and sugar until light and fluffy, about 3 minutes.
Beat in eggs one at a time, then stir in the mashed bananas and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, alternating with buttermilk, beginning and ending with the dry ingredients. Mix just until incorporated after each addition.
Pour the batter into the prepared pan and smooth the top with a spatula.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Cool the cake completely in the pan on a wire rack before frosting.
If making cream cheese frosting: Beat cream cheese and butter until smooth. Gradually add powdered sugar, vanilla, and salt. Beat until fluffy, about 3 minutes.
Spread frosting evenly over the cooled cake and serve.