Line a baking sheet with parchment paper or a silicone baking mat.
In a small bowl, mix together flour, baking powder, baking soda, salt, and set aside.
If using cinnamon and sugar topping, mix together in a bowl and set aside.
Using a standing mixer, or hand held mixer with a large bowl, cream butter and sugar until light and fluffy, around 2-3 minutes.
Mix in egg and vanilla extract until combined.
Then, alternate mixing in dry ingredients with sour cream, in two to three parts (beginning and ending with dry ingredients).
Using a tablespoon or small ice cream scoop, drop 1-2 tablespoon sized balls of cookie dough onto the prepared baking sheet, leaving about 2 inches in between each cookies.
For a flatter cookie, gently pat the cookies flat using a slightly wet finger.
If using sugar topping or sprinkles, sprinkle mixture on top of cookies.
Bake in preheated oven for 10-12 minutes or until edges are very lightly browned. Remove from oven and let cool on baking sheet.
Once the cookies are cooled, add any optional frosting and enjoy!
Notes
If not using a scale, be sure to measure out the flour using the spoon and swipe method of fluffing up the flour and then spooning into the measure cup and swiping the excess off the top with a knife.
A small ice cream scoopworks great for getting even sized cookies.
For flatter cookies, gently tap down the top of the cookie with a slightly wet finger or spatula before baking.
Be sure to let the baked cookies cool completely before adding any frosting, otherwise the warm cookies will make the frosting melt.
The cookies will last 3-5 days in an airtight container at room temperature. Baked and unfrosted cookies can be frozen up to two months.