Combine the butter and sugar in a medium-size skillet. Place the pan over low heat on top of the stove, and cook, stirring, until the sugar dissolves.
Place the bananas in the pan. When the banana slices soften and begin to brown, carefully add the rum. Continue to cook the sauce until the rum is hot, then tip the pan slightly to ignite the rum. When the flames subside, spoon the bananas out of the pan and over slices of Peanut Butter Bread.
Generously spoon warm sauce over the top of the ice cream and serve immediately. Add a scoop of vanilla if desired.
* You can use pound cake or banana bread for the Peanut Butter Bread