1. Preheat your oven to 350°F (175°C).
2. In a bowl, whisk together flour, baking powder, baking soda, and salt.
3. In another bowl, cream together the softened butter and granulated sugar until light and fluffy.
4. Add the egg and vanilla extract to the butter mixture and mix well.
5. Stir in the sour cream until combined.
6. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
7. In a small bowl, mix together the brown sugar and cinnamon.
8. Drop spoonfuls of the cookie dough onto a baking sheet lined with parchment paper.
9. Sprinkle the cinnamon sugar mixture over the top of each cookie.
10. Bake for 10-12 minutes or until the edges are lightly golden.
11. Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.

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