Preheat your oven to 350°F (175°C) and grease your bundt pan well to ensure easy release after baking.

In a mixing bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.

In another bowl, use an electric mixer to cream the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

Alternate adding the dry mixture and buttermilk to the butter mixture, beginning and ending with the flour mixture.

Pour half of the batter into your prepared pan and sprinkle with half of the cinnamon swirl mixture.

Pour remaining batter over the top and finish with the rest of the swirl mixture.

Using a knife or skewer, gently swirl through the batter to create a cinnamon pattern.

Bake for 50-60 minutes or until a toothpick inserted in the center comes out clean.

Allow the cake to cool in the pan for about 10 minutes before inverting it onto a wire rack to cool completely.