Preheat the oven to 350°F (175°C) and grease a Bundt pan well.

In a medium bowl, whisk the flour, baking powder, and baking soda together.

In a large mixing bowl, beat the softened butter and sugar until fluffy and light in color.

Add the eggs one at a time, mixing until fully incorporated before adding the next.

Stir in the sour cream and vanilla extract until the batter is smooth.

Gradually add the flour mixture, mixing just until no dry flour remains.

In a small bowl, combine the cinnamon and brown sugar.

Spoon half the batter into the Bundt pan, sprinkle half the cinnamon-sugar mixture, then layer with the remaining batter and top with the rest of the cinnamon-sugar.

Use a knife to swirl through the batter lightly.

Bake in the preheated oven for 50–60 minutes, or until a toothpick comes out clean.

Allow the cake to cool in the pan before inverting onto a plate.