Preheat your oven to 375°F and line a baking sheet with parchment paper.
With a handheld mixer, or stand mixer, beat the butter and brown sugar until light and fluffy.
Add the egg and vanilla extract and beat until blended.
In a mixing bowl, combine the flour, baking soda, cornstarch, salt, and ground cinnamon, whisking until blended.
Gradually add the flour mixture to the butter mixture and beat until a cookie dough forms.
Place the cinnamon sugar in a small bowl.
Using a #40 size scooper, scoop the dough and roll in the cinnamon sugar to coat the cookie dough.
Arrange the cookie dough on the prepared baking sheet about 2-inches apart and bake, in batches, for 12 minutes or until the edges are set.
Allow the cookies to cool on the baking sheet for about 3 minutes before transferring to a wire rack to cool or eat them warm!