Preheat the oven to 325°F. Grease a 12-cup bundt pan with butter and dust with flour, shaking off excess.
In a bowl, whisk together cake flour, baking soda, and salt. Set aside.
With a hand mixer or stand mixer with a paddle attachment, beat the butter for one minute.
Add the cream cheese and beat for 30 seconds. Scrape the bowl.
Add the sugar and beat for 2 minutes, scraping the bowl halfway.
Add eggs one at a time, mixing until incorporated before adding the next. Scrape the bowl between additions.
Mix in vanilla extract.
Add half of the flour mixture and mix on low to combine.
Add the buttermilk and mix until incorporated.
Add the remaining flour mixture and mix just until combined.
Pour the batter into the greased and floured pan.
Bake for 65 to 80 minutes. Start checking at 55 minutes. The cake is done when a toothpick inserted comes out clean, the top is not jiggly, and it springs back slowly when poked.
Let the cake cool in the pan for at least 1 1/2 hours. Only remove it from the pan when completely cooled.