How to Make It
Puree the banana in a food processor until very smooth.
Cook the sugar and ½ cup water in a medium pot over medium heat, stirring, until the sugar is just dissolved, 2 to 3 minutes. Continue to cook, without stirring, until the syrup is a dark golden brown, 14 to 16 minutes more. (If dark spots start to appear in the sugar mixture, gently swirl the pan to incorporate.)
Remove from heat and carefully add the vanilla, salt, and banana puree (the mixture will sputter); stir until combined.