Preheat your oven to 350 degrees F. Grease your Bundt pan very thoroughly with softened butter or baking spray, making sure to get into every ridge and the center tube. Then dust lightly with flour, tapping out any excess. This step is not optional. A well-greased pan is the difference between a beautiful release and a frustrating mess.

Make the cream cheese swirl. Beat the softened cream cheese and 1/3 cup granulated sugar together until smooth and creamy, about 2 minutes. Add the egg yolk and vanilla and beat until combined. Set aside.

Whisk the flour, baking soda, salt, cinnamon, ginger, nutmeg, and allspice together in a large bowl. In a separate large bowl, whisk the pumpkin puree, granulated sugar, brown sugar, eggs, vegetable oil, and sour cream together until smooth and well combined.

Add the dry ingredients to the wet ingredients and stir with a rubber spatula until just combined and no dry streaks remain. Do not beat or overmix.

Pour slightly more than half of the pumpkin batter into the prepared Bundt pan and spread it into an even layer. Spoon the cream cheese mixture over the batter in a ring, keeping it away from the edges of the pan so it stays tucked inside the cake as it bakes. Drop the remaining pumpkin batter over the cream cheese and spread gently to cover.

Bake for 55 to 65 minutes, until a toothpick inserted into the pumpkin portion comes out clean or with a few moist crumbs. The top of the cake (which will become the bottom once flipped) should feel set and spring back lightly when pressed. Do not underbake or the cake will stick and tear when you flip it.

Let the cake cool in the pan on a wire rack for exactly 15 minutes. No longer, or steam will cause it to stick. Place your serving plate upside-down over the pan, then flip both together in one confident motion. Lift the pan away. If the cake sticks in a spot, tap the pan gently. Let the cake cool completely on the rack, at least 1 hour.

Stir together the powdered sugar and 1 teaspoon cinnamon. When the cake is fully cool, use a fine mesh sieve to dust the top evenly with the spiced sugar mixture. Serve in thick slices.