Preheat the oven to 350 degrees F (180°C) with oven rack in the center of oven.

Combine Wet Ingredients: Whisk the milk, sour cream and rum together in a liquid measure and let come to room temperature.

Cream butter and sugar: In a large bowl or stand mixer whip the butter on medium speed for 1 minute. Add the granulated sugar and beat for 3-4 minutes until light and fluffy. Add vanilla. Add eggs and egg yolks, one at a time, mixing just between additions. Scrape down the sides of the bowl.

Mix Dry Ingredients: Combine the cake flour, baking powder, baking soda and salt.

Alternate Ingredients: Add ⅓ of the dry ingredients to the batter and mix just until combined. Add ½ of the milk/sour cream mixture and mix. Add another ⅓ of the dry ingredients, mixing just until combined. Add the last ½ of the milk/sour cream mixture and beat until just combined. Add the final ⅓ of the dry ingredients and mix just until combined, scraping down the sides of the bowl.

Bake: Grease and flour bundt pan. Pour batter evenly into the pan and bake at 350 degrees F for about 50 minutes or until a toothpick inserted in the center comes out clean, or with few crumbs.

Glaze: Add glaze ingredients to a saucepan over medium heat. Stir well until butter has melted and mixture is smooth. Bring mixture to a boil, stirring, and boil for 2 minutes.

Finish Cake: Allow the cake to cool in the pan for 15 minutes before gently inverting it. Poke holes all over the cake and gently pour most of the glaze over the cake, reserving just a little.

Serve: Allow the cake to soak up the glaze and then invert it onto a plate or serving platter. Spoon remaining glaze on top before serving.