Preheat oven to 350 ℉.
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!