The cake bakes right to the edge (pictured above) of a 6-cup pan which can make some bakers a bit nervous. If that’s you, bump up to a 7-cup bundt pan. I’ve also had success using a 1-lb loaf pan (8.5-inch x 4-1/2-inch) for this cake, but you will need to bake the cake significantly longer for the middle to set.
Combine the 1/3 cup sugar with 1/3 cup water in a small sauce pan over medium heat. Bring to a simmer and stir until sugar is dissolved. Remove from heat, stir in the rum and allow to cool to room temperature while you work on the rest of the cake.
Prepare the pan. Butter and flour (or coconut flake) a 6-cup bundt pan (see the head notes for alternate pan size ideas). Set prepared pan aside.