Combine butter, shortening, and sugar in the bowl of an electric mixer (or mixing bowl and hand mixer). Beat well, until blended.
Add eggs, one at a time, mixing thoroughly between additions.
Add flour. Combine. Add buttermilk. Combine.
Next, add baking soda, salt, baking powder, and vanilla extract. Mix to combine.
Lastly, beat in the rum and pour into a buttered and floured bundt pan.
Bake at 350 degrees F. for 1 hour or until a toothpick inserted in the center comes out clean.
For the Rum Glaze
Combine all ingredients in a sauce pan and bring to a boil. Spoon over the cake while still warm.
For the Rum Icing Glaze
Make a second batch of the rum glaze. Allow it to cool and whisk it with powdered sugar until it's a pourable icing consistency. Add more powdered sugar for a thicker icing. Drizzle over cake. Enjoy!