Step 1: Preheat your oven to 325°F (160°C). Grease and flour a 10-12 cup Bundt pan thoroughly. Make sure to get into all the crevices.
Step 2: In a large mixing bowl, cream together the softened butter and softened cream cheese with an electric mixer on medium speed until light and fluffy, about 3-5 minutes.
Step 3: Gradually add the granulated sugar, about 1/2 cup at a time, beating well after each addition until the mixture is pale and fluffy, another 5-7 minutes. Scrape down the sides of the bowl as needed.
Step 4: Add the eggs one at a time, beating well after each addition. Ensure each egg is fully incorporated before adding the next. The mixture might look slightly curdled, which is normal.
Step 5: In a separate bowl, whisk together the sifted all-purpose flour, baking powder, and salt.
Step 6: With the mixer on low speed, gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Begin and end with the dry ingredients (e.g., 1/3 flour, 1/2 buttermilk, 1/3 flour, 1/2 buttermilk, 1/3 flour). Mix only until just combined and no streaks of flour remain. Do not overmix.
Step 7: Stir in the vanilla extract until fully incorporated.
Step 8: Pour the batter evenly into the prepared Bundt pan. Tap the pan gently on the counter a few times to release any air bubbles.
Step 9: Bake for 1 hour 20 minutes to 1 hour 30 minutes, or until a wooden skewer or toothpick inserted into the center of the cake comes out clean. The top should be golden brown and spring back when lightly touched.
Step 10: Remove the cake from the oven and let it cool in the pan on a wire rack for 15-20 minutes. This allows the cake to firm up before inverting.
Step 11: After cooling slightly, carefully invert the cake onto a wire rack to cool completely before slicing and serving.