Simmer brown sugar, butter, rum, liqueur, cinnamon and salt in a large saute pan over medium heat. Cook until thickened, about 8 minutes, whisking occasionally.
Add bananas and simmer until warmed through, about 1 minute.
Take off of the heat and stir in pineapple.
Cut shortcakes in half horizontally. Coat cut sides of each shortcake with Foster sauce. Place bottoms on serving dishes, cut side up, then top with fruit mixture, ice cream, nuts and remaining shortcake halves.