First, preheat the oven to 375°F. Prepare a non-stick cookie sheet with parchment paper.
Next, in a medium bowl, whisk together the flower, baking powder, and salt. Set aside.
Moreover, in your stand mixer bowl with the paddle attachment, cream together the butter, granulated sugar, and brown sugar on medium-low speed until well-blended, about 1-2 minutes.
Similarly, mix in the egg and vanilla.
Further, add sour cream and mix until well-blended.
Next, set the mixer to low speed. Slowly add in the dry ingredients, mixing just until they are blended in.
Then, with your hands buttered, scoop the dough out in 1 tablespoon portions and roll each into a ball.
Place each ball on the cookie sheet.
Bake in the preheated oven for about 15 minutes until the bottoms are a light golden brown. Transfer them to a cooling rack and allow them to cool.