To Make the Batter in a Stand Mixer:

1. Preheat oven to 325°F.  It is highly recommended to use an oven thermometer for this recipe, since proper oven temperature can impact the finished product.
2. Combine the buttermilk and rum in a two-cup liquid measuring cup.
3. In a medium bowl, combine the flour, baking soda and salt (if using kosher salt, omit it from this step).
4. Sift the flour/baking soda mixture into a large bowl.  If using kosher salt, add it at this time.
5. Place the room temperature butter in the bowl of your stand mixer.  Mix on low speed until smooth.  (30 seconds)
6. Slowly add the granulated sugar and brown sugar and mix on medium speed until the mixture is light and fluffy.  (7-10 minutes)
7. Add eggs, one at a time, mixing for at least 45 seconds after each addition.  Scrape the bowl as needed (I usually scrape the bowl after the third and fifth egg).  This step is extremely important because eggs help with cake rise!  (6 minutes)
8. Add vanilla extract and rum extract (if using) and mix until thoroughly combined.  (1 minute)
9. Add half of the flour mixture and mix on low speed until combined. (30-45 seconds)
10. Add all of the buttermilk/rum mixture and mix on low speed until well combined.  (~1 minute)
11. Add the second half of the flour mixture and mix on low speed until almost combined.  Stop mixing just before the mixture is fully together. (1-2 minutes)
12. Using a rubber spatula, fully scrape the sides and bottom of the mixing bowl.  Keep mixing until the batter is smooth and consistent.  Make sure to get the entire bottom of the bowl!
13. Grease a 10-12 cup bundt pan with butter and flour and place the batter in the pan.

To Make the Batter with a Hand Mixer:

1. Preheat oven to 325°F.  It is highly recommended to use an oven thermometer for this recipe, since proper oven temperature can impact the finished product.
2. Combine the buttermilk and rum in a two-cup liquid measuring cup.
3. In a medium bowl, combine the flour, baking soda and salt (if using kosher salt, omit it from this step).
4. Sift the flour/baking soda mixture into a large bowl.  If using kosher salt, add it at this time.
5. Place the room temperature butter in the a large mixing bowl.  Mix on low speed until smooth.  (~1 minute)
6. Add half of the sugar and mix until the sugar is incorporated.  (~30 seconds)
7. Add the second half of the sugar and mix on medium speed until the mixture is light and fluffy.  (9-12 minutes)
8. Add eggs, one at a time, mixing for at least 1 minute after each addition.  Scrape the bowl as needed (I usually scrape the bowl after the third and fifth egg).  This step is extremely important because eggs help with cake rise!  (7 minutes)
9. Add vanilla extract and rum extract (if using) and mix until thoroughly combined.  (1 minute)
10. Add half of the flour mixture and mix on low speed until combined. (~1 minute)
11. Add all of the buttermilk/rum mixture and mix on low speed until well combined.  (~1 minute)
12. Add the second half of the flour mixture and mix on low speed until almost combined.  Stop mixing just before the mixture is fully together. (1-2 minutes)
13. Using a rubber spatula, fully scrape the sides and bottom of the mixing bowl.  Keep mixing until the batter is smooth and consistent.  Make sure to get the entire bottom of the bowl!
14. Grease a 10-12 cup bundt pan with butter and flour and place the batter in the pan.

To Bake the Cake:

1. Bake the cake at a true 325°F for 60-75 minutes, or until an instant read thermometer reads 210°F-215°F.  My preferred internal temperature is 212°F on the nose.  Alternately, the cake is done when a toothpick inserted into the center comes out with just a few crumbs.
2. Allow the cake to rest for ten minutes while you make the simple syrup.

To Make the Butter Rum Simple Syrup:

1. Combine water, sugar, vanilla and salt in a small sauce pan.
2. Bring the mixture to a boil, then whisk occasionally until the sugar is completely dissolved.
3. Remove from the heat and add rum and butter.   Stir gently until the butter is completely melted.  This recipe makes enough butter rum simple syrup to brush the cake one time.
4. After allowing the cake to rest for ten minutes, invert it on a cooling rack and carefully remove the bundt pan.
5. Using a pastry brush, gently brush the butter rum simple syrup over the entire cake.  This step can be repeated multiple times while the cake is warm.  It’s recommended to wait about ten minutes between simple syrup layers.
6. If you’re trying to make a more boozy rum cake, you can poke holes in the top of the cake and pour the butter rum simple syrup directly over the holes.  I would only recommend doing this once though.
7. Allow the cake to cool completely. (3-5 hours)

To Make the Final Glaze:

1. Combine confectioner’s sugar, salt, vanilla, and rum in a medium bowl.
2. Combine the mixture and stir until combined but lumpy.
3. Add heavy cream and stir until smooth.  The mixture should just be pourable.  If it is still too thick to pour once it’s combined, add heavy cream, 1 tsp at a time until it is smooth enough to pour.
4. Final glaze should have the consistency of thick honey.
5. Using a spouted measuring cup, spoon, or squeeze bottle, pour final glaze over the cake.  If necessary, use a spoon to help the glaze fall over the sides of the cake.