Pre-heat the oven to 350-degrees
Spray a 9x13 pan heavily with cooking spray or grease.
In a small sauce pan melt 3 Tbsp of butter over medium heat, stirring throughout until the butter begins to turn brown, but DO Not burn. The aroma will be strong. Remove from heat and transfer the browned butter to a large mixing bowl.
Add brown sugar, honey, mashed bananas and vanilla. Mix well.
Stir in buttermilk, eggs and oil.
In another bowl combine flour, salt, and baking soda ans whisk to combine.
Add dry ingredients to wet ingredients and mix until incorporated. Pour into prepared pan and bake for 35-45 minutes, until a toothpick comes out clean. Remove from oven and allow to cool completely.
Prepare the frosting (below) - and spread onto the cake after it has cooled. Allow the frosting to set before slicing and serving. Store in an air-tight container at room temp.