Preheat the Oven:
Preheat your oven to 350°F (175°C). Grease a Bundt pan with butter or non-stick spray.

Cream the Butter and Sugar:
In a large mixing bowl, cream together the butter and sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

Prepare the Dry Ingredients:
In a separate bowl, whisk together the flour, baking soda, and baking powder.

Combine the Ingredients:
Gradually add the dry ingredients to the butter mixture, alternating with sour cream. Begin and end with the dry ingredients. Mix until just combined.

Assemble the Cake:
Layer half of the batter into the greased Bundt pan. In a small bowl, mix the ⅓ cup granulated sugar and cinnamon together for the swirl. Sprinkle half of the cinnamon-sugar mixture over the batter. Add the remaining batter on top, then sprinkle with the rest of the cinnamon-sugar. Gently swirl the batter with a knife to create the cinnamon swirl.

Bake:
Bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean.

Cool and Invert:
Let the cake cool in the pan for about 10 minutes, then invert onto a serving plate. Allow to cool completely before slicing and serving.