I guessed this recipe would be awesome from the start, and it totally exceeded my expectations!

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
In a large bowl, cream together the softened butter and sugar until light and fluffy, about 3 minutes.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the sour cream until the dough is smooth and well mixed.
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

Variations & Tips
For a festive touch, you can sprinkle the tops of the cookies with colored sugar or sprinkles before baking. If you prefer a citrusy flavor, try adding a teaspoon of lemon or orange zest to the dough. For a richer taste, you can substitute half of the granulated sugar with brown sugar. These cookies can also be iced with a simple glaze made from powdered sugar and milk for added sweetness.