If making the buttercream frosting, take the butter for the frosting out of the refrigerator and allow it to come to room temperature while baking the cookies. Preheat the oven to 350 degrees Fahrenheit.
In a medium sized mixing bowl, combine the flour, baking powder, and cinnamon. Remember to measure the flour using the scoop & level method which is explained above.
In a stand mixer, combine the cold, cubed butter with the granulated sugar and brown sugar. Mix with the paddle attachment until creamed together.
Add the egg and vanilla extract to the mixing bowl and mix until combined.
Slowly add in the flour mixture until the dough forms a ball. If the dough is too sticky to form a ball, add a bit of flour. If the dough is crumbly, that is okay, use your hands to mix the dough until it resembles a ball.
Roll the cookies out to 3/8" onto a floured surface or a piece of parchment paper. Cut the cookies using a cookie cutter and bake on a prepared cookie sheet for 7-10 minutes or until the top of the cookie doesn't look wet.