Preheat your oven to 350°F (175°C) and grease a bundt pan.
In a large bowl, mix together flour, baking powder, baking soda, and salt.
In another bowl, combine sugar, eggs, melted butter, sour cream, and vanilla extract.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
In a small bowl, mix brown sugar and cinnamon.
Pour half of the batter into the prepared bundt pan.
Sprinkle half of the cinnamon sugar mixture over the batter.
Add the remaining batter and top with the remaining cinnamon sugar mixture.
Bake for 40-45 minutes or until a toothpick comes out clean.
Let the cake cool for 10 minutes before inverting onto a serving plate.