Preheat your oven to 325°F. Liberally prepare a 12-cup Bundt pan with the nonstick method of your choice. (I recommend the shortening and flour method to make sure this cake doesn’t stick as the swirl sugar mixture can sometimes sink a little to the bottom).
In the bowl of your stand mixer fitted with the whisk attachment, beat the butter for 1 minute on high speed. Slowly add the granulated sugar. Cream together for an additional 5 minutes, until very pale yellow and fluffy. Add the eggs 1 at a time, combining well after each addition and scraping down the sides and bottom of the bowl as needed.
Turn your mixer down to its lowest speed and slowly add the flour in 2 batches. Add the salt and baking soda. Be careful not to overbeat. Add the sour cream, oil, and vanilla extract. Scrape down the sides and bottom of the bowl and mix the batter until just combined. Be careful not to overmix. Set the batter aside.
For the Cinnamon Swirl
In a small bowl, whisk together all the ingredients until well combined. Set aside.
To Bake
Pour ⅓ of the batter into the prepared pan.
Drizzle ½ of the cinnamon swirl over the batter. Using a butter knife or skewer, swivel the mixture through the cake batter, creating a flourish pattern.
Repeat with the next 1/3 of the cake batter and cinnamon swirl. Top with the remaining batter. Bake for 85 to 95 minutes, or until a toothpick inserted into the center of the cake comes out mostly clean.
Let the cake cool in the pan on a wire rack for 10 minutes, then invert onto a serving plate. Let cool to room temperature. Lightly cover the cake with foil or plastic wrap so it does not dry out.
For the Icing
Clean your stand mixer bowl and whisk attachment. Beat the cream cheese and butter for 2 minutes on medium-high speed.
Reduce your mixer speed and carefully add the confectioners’ sugar in 2 batches, scraping down the sides and bottom of the bowl as needed. Once the sugar is fully incorporated, turn your mixer back up to medium-high speed. Add the milk and vanilla extract and beat until the icing is smooth and pourable.
Drizzle the icing over the cooled pound cake. Serve at room temperature.