Add butter to a preheated large non stick skillet. Add brown sugar and stir until it begins to soften into butter. Allow to cook 1 minute.
Add cinnamon and chopped walnuts. Stir and cook 1 minute.
Clear a space in the center and add bananas cut side down. Cook for 1 minute.
Add rum around the exterior of pan to soften sauce and cook for 2 minutes.
Optional: ignite the rum with a long handled match and shake pan until flames die out.
Serve immediately over vanilla ice cream or with whipped cream.
**Note: Bananas on the just still green side hold up the best texture wise. But any ripeness can be used.