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 ground cinnamon. Set aside.

In a large bowl, beat the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes. 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 buttermilk. Begin and end with the flour mixture, mixing until just combined.

In a small bowl, combine the ground cinnamon and sugar for the swirl.

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

Bake for 45-50 minutes or until a toothpick inserted in the center comes out clean. Allow the cake to cool in the pan for 10 minutes before inverting onto a wire rack to cool completely.