In a small saucepan, combine the rum, vanilla extract, brown sugar, molasses and cinnamon. Bring the mixture to a simmer and stir to dissolve the brown sugar. Shut off the heat and keep warm on the stove.
Heat a cast iron skillet over medium heat. When the skillet feels pretty hot, add the butter and allow it to brown slightly. Toss in the bananas and arrange them, with a wooden spoon, in a single layer in the pan. Sprinkle with a tiny pinch of salt and cook for about 30 seconds to 1 minute. Turn them on their second side and cook for an additional 30 seconds. Pour in the rum mixture and stir to coat. Serve immediately with vanilla ice cream.
Recipe courtesy Alex Guarnaschelli