Preheat the oven to 325°F (163°C), not 350°F. Generously grease a 10-12 cup Bundt pan with butter or nonstick spray.
Using a handheld or stand mixer with a paddle or whisk attachment, beat the butter on high speed until smooth and creamy, about 2 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula. Add the cream cheese and beat on high speed until completely smooth and well combined, about 1 minute. Then, add the sugar and beat on high speed until combined, about 1 minute. Next, add the sour cream and vanilla and beat on high speed until well incorporated and creamy. Scrape down the sides and bottom of the bowl with a silicone spatula.
On low speed, add the eggs one at a time, allowing each egg to fully mix in before adding the next. Be careful not to overmix once the eggs are added. Once the 6th egg is fully combined, stop the mixer and add the cake flour, baking powder, and salt. Beat on medium speed just until combined—do not overmix. Using a silicone spatula or a sturdy whisk, give the batter a final stir to ensure there are no lumps at the bottom of the bowl. The batter will be thick and creamy.
Pour or spoon the batter evenly into the prepared pan. Tap the pan on the counter once or twice to release any air bubbles. Bake for 75-95 minutes, loosely tenting the cake with aluminum foil halfway through the baking time to prevent the surface from over-browning. The key to a perfect pound cake is a slow and low baking time. Use a toothpick to test for doneness—once it comes out completely clean, the cake is done. This is a large, heavy cake, so don’t worry if it takes longer in your oven. If needed, continue baking until fully done.
Remove the cake from the oven and let it cool for 2 hours inside the pan. Then, invert the slightly cooled cake onto a wire rack or serving dish. Allow the cake to cool completely.
Slice and serve with optional toppings such as homemade whipped cream and fresh berries.
Store any leftover cake tightly covered at room temperature for up to 2 days or in the refrigerator for up to 5 days.