Preheat your oven to 350°F (175°C); then, grease and flour a 9x13 inch baking pan.

In a medium bowl, whisk together the flour, baking soda, salt, and cinnamon until well combined.

In a large bowl, cream together the softened unsalted butter and granulated sugar until the mixture is light and fluffy.

Beat in the eggs one at a time; then, stir in the vanilla extract and mashed ripe bananas.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, ensuring to begin and end with dry ingredients; mix until just combined.

Pour the batter evenly into the prepared baking pan.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center of the cake comes out clean.

Allow the cake to cool completely in the pan on a wire rack before frosting or serving.