Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt. Set aside.
In a large bowl, using an electric mixer, beat the softened unsalted butter and granulated sugar together on medium speed until creamy and light in color, about 2-3 minutes.
Add the egg and pure vanilla extract to the butter mixture and beat until fully combined.
Mix in the sour cream until smooth.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until combined. Do not overmix.
Scoop tablespoon-sized portions of dough and roll each into a ball. Roll each ball in granulated sugar to coat generously.
Place the sugar-coated dough balls onto the prepared baking sheets about 2 inches apart to allow for spreading.
Bake in the preheated oven for 9-11 minutes, or until the edges are set and just beginning to turn golden but the centers still look soft.
Remove from the oven and allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Store cooled cookies in an airtight container at room temperature for up to 5 days.