In a large skillet, melt the butter over medium heat.
Stir in the brown sugar and cinnamon, cooking until the mixture is bubbly and well combined, about 2-3 minutes.
Add the sliced bananas to the skillet and gently toss to coat them in the sauce. Cook for about 2-3 minutes until the bananas are heated through and slightly softened.
Carefully add the dark rum and vanilla extract to the skillet. If desired, carefully ignite the rum with a long lighter to flambé the mixture, allowing the flames to subside naturally. If you prefer not to flambé, simply stir to combine.
Remove the skillet from heat and serve the warm banana mixture over scoops of vanilla ice cream.
Garnish with chopped walnuts or pecans if desired.