8. Prepare Syrup
Meanwhile, make the citrus-rum syrup. Melt the butter in a medium saucepan over medium heat, then, when the butter is foamy, stir in the sugar and orange juice. Bring to a boil. Continue to boil, stirring constantly, for 5 minutes.
Remove the pan from the heat and add the rum. Return the pan to medium heat and cook, stirring, for 30 more seconds, then remove from the heat and set aside.