Preheat your oven to 375 degrees. Prep a large jelly roll pan and set aside.
Combine the sugar and butter in a mixing bowl. Whisk 1 minute or until light and fluffy. Add the sour cream and stir until combined.
Add the eggs, one at a time, along with the vanilla extract. Stir in the mashed bananas.
Whisk in the flour, salt, and baking soda. Stir until fully incorporated. Spread into your prepared pan and bake 20-25 minutes or until a toothpick comes out clean.
For the frosting:
Add the butter to a pot. Cook, mixing occasionally, until the butter turns a light brown color. Remove from the heat.
Whisk in the powdered sugar, vanilla, and milk until smooth. Spread onto a cooled cake.