Preheat the oven to 375 degrees F. Line one large or two standard sheet pans with parchment paper.
In a medium-sized bowl, whisk together the flour, baking powder, salt, and cinnamon.
Using either a stand mixer with the paddle attachment or an electric mixer, cream the butter and sugar together until smooth and fluffy, 2-3 minutes. Add in the egg and vanilla, and mix on medium-high speed until fully combined. Scrape the bowl, all the way to the bottom. Finally, add the flour mixture, mixing until completely combined.
Cover the bowl with the cookie dough and place in the refrigerator for 10-15 minutes, until slightly firmed up.
To prepare the coating, place the sugar and cinnamon in a small bowl.
Using a tablespoon-sized cookie scoop, portion out the dough, briefly shape into balls, then drop into the coating (you can do a few at a time). Swirl the bowl around until the balls are completely coated, then place 1 1/2 inches apart on the prepared baking sheets.
Use a flat-bottomed glass to flatten the cookies until they’re around 1 1/2 inches in diameter.
Bake for 8 minutes if you prefer soft and chewy cookies, or approximately 10 minutes for crunchier cookies. Remove from the oven, cool for 5 minutes, then to transfer to a cooling rack.
Store in an airtight container at room temperature for up to three days, in the refrigerator for up to one week, or in the freezer for up to 3 months.