Preheat oven to 350°F (175°C). Grease a 9x13 inch pan.

In a large bowl, mix melted/browned butter with sugars. Whisk in eggs one at a time, then add mashed bananas and vanilla.

In a separate bowl, sift together flour, baking soda, salt, and cinnamon.

Add the dry ingredients and buttermilk to the wet mixture, starting and ending with dry. Mix until just combined; do not over-mix.

Pour into the pan. Bake for 35-40 minutes, or until a toothpick comes out clean. Let it cool completely before frosting.

Make the Salted Caramel Sauce: Heat sugar in a medium saucepan over medium heat, stirring constantly with a wooden spoon until it melts into a thick, amber-colored liquid.

Carefully whisk in the butter until melted. Be cautious as the mixture will bubble up rapidly.

Slowly pour in the heavy cream while whisking. Let it softly boil for 39 seconds, then remove from heat.

Stir in the salt. Pour into a glass jar and let it cool completely at room temperature (or in the fridge) until thickened.

Whip the Frosting: In a large bowl, beat the softened butter and cream cheese together until very smooth and fluffy (about 2–3 minutes).

Mix in ½ cup of your cooled caramel sauce and the vanilla until fully incorporated.

Gradually add powdered sugar one cup at a time on low speed until you reach your desired spreading consistency.

Increase the speed to medium-high and beat for 2 minutes until light and airy.

After spreading the frosting over your cooled banana cake, use a spoon to drizzle any remaining caramel sauce over the top and swirl it in with a knife for a marbled look.