Preheat your oven to 350°F (175°C). Grease and flour a 10-inch Bundt pan.

In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and 1 teaspoon of cinnamon. Set aside.

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

Gradually add the dry ingredients to the butter mixture, alternating with the sour cream, starting and ending with the flour mixture. Mix until just combined.

In a small bowl, combine the brown sugar and 1 tablespoon of cinnamon to create the cinnamon swirl mixture.

Pour half of the cake batter into the prepared Bundt pan. Sprinkle half of the cinnamon swirl mixture over the batter. Pour the remaining batter on top and finish with the rest of the cinnamon swirl mixture. Use a knife to gently swirl the batter for a marbled effect.

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.