Preheat oven to 350°F.

In a 10-inch cast-iron skillet, melt the butter over medium-high heat. Once the butter is melted, add in the brown sugar and stir until it melts. Add in the bananas and cook until they begin to caramelize, about 2 minutes. Once they begin to caramelize, turn off the heat, add in the milk and let cool for about 10 minutes.

Once cool, add in the eggs and whisk until smooth and combined. Whisk in the cinnamon, baking powder and salt. Using a rubber spatula, mix in the flour 1/2 cup at a time. Once you’ve added all the flour, fold in the walnuts.

Transfer skillet to the oven and bake for 25-30 minutes or until cake has risen and a toothpick poked in the middle of the cake comes out batter-free. Remove from oven and let cool.

Once cool, spread frosting over to top, slice and serve.