Prepare Bundt Pan: Grease the Bundt pan with non-stick spray or butter and flour. Preheat oven to 350°F (175°C).

Mix Batter: Cream butter and sugar until fluffy. Add eggs one at a time.

Combine Dry Ingredients: Whisk flour, baking powder, baking soda, cinnamon, and salt in a separate bowl.

Combine Wet Ingredients: Gradually mix dry ingredients into creamed mixture, alternating with sour cream.

Layer the Batter: Pour half the batter into the pan and sprinkle with half the cinnamon sugar mix, then add remaining batter.

Create the Swirl: Use a knife to make figure-eight motions for swirling cinnamon sugar into the batter.

Bake: Bake for about 50 minutes or until golden brown and a toothpick comes out clean.

Cool: Let cake cool in the pan for 15 minutes before inverting onto a wire rack.