Step 1: Prepare Your Pan
Preheat your oven to 325°F (165°C). Generously grease a 10-12 cup bundt pan with butter or non-stick spray, making sure to coat every ridge and crevice. If using pecans, sprinkle them evenly in the bottom of the greased pan. This attention to greasing is crucial—you want this cake to release perfectly.

Step 2: Mix Dry Ingredients
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set this aside. Whisking aerates the flour and ensures the leaveners are evenly distributed throughout.

Step 3: Cream Butter and Sugar
In a large mixing bowl using an electric mixer, cream the room temperature butter and sugar together on medium-high speed for 3-4 minutes until the mixture is light, fluffy, and pale yellow. This step incorporates air into the batter, which helps create a tender crumb. Don’t rush this—proper creaming is essential.

Step 4: Add Eggs
Add the eggs one at a time, beating well after each addition. Make sure each egg is fully incorporated before adding the next. The mixture should look smooth and emulsified. If it looks slightly curdled, that’s okay—it’ll come together when you add the dry ingredients.

Step 5: Combine Wet Ingredients
In a small bowl or measuring cup, whisk together the sour cream, milk, and vanilla extract until smooth.

Step 6: Alternate Adding Ingredients
With your mixer on low speed, add the flour mixture in three additions, alternating with the sour cream mixture in two additions. Begin and end with the flour mixture. The pattern should be: flour, sour cream, flour, sour cream, flour. Mix just until combined after each addition—overmixing develops gluten and creates a tough cake. Use a rubber spatula to scrape down the sides and bottom of the bowl to ensure everything is incorporated.

Step 7: Bake the Cake
Pour the batter into your prepared bundt pan, smoothing the top with a spatula. Tap the pan gently on the counter 2-3 times to release any air bubbles. Bake for 50-60 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter). The top should be golden brown and spring back when lightly touched.

Step 8: Make the Rum Glaze
While the cake is baking, prepare your glaze. In a medium saucepan over medium heat, combine the butter, sugar, water, and rum. Bring to a boil, stirring constantly to dissolve the sugar. Once boiling, reduce heat to low and simmer for 5 minutes, stirring occasionally. The mixture will thicken slightly and become syrupy. Remove from heat and stir in the vanilla extract.

Step 9: Initial Glaze Application
When the cake comes out of the oven, let it cool in the pan for 10 minutes. Using a wooden skewer or toothpick, poke holes all over the bottom of the cake (which will become the top when inverted). Slowly brush or pour about one-third of the warm glaze over the cake while it’s still in the pan. Let it absorb for 5 minutes.

Step 10: Invert and Finish Glazing
Carefully invert the cake onto a wire rack set over a baking sheet or large plate (to catch drips). Remove the pan slowly. While the cake is still warm, poke more holes all over the top and sides with your skewer. Slowly brush the remaining glaze all over the cake, allowing each application to soak in before adding more. Use all the glaze—this is what makes rum cake so incredibly moist! Let the cake cool completely before slicing.