Whisk the flour, baking soda and salt together in a medium bowl and set aside.
Combine the butter and sugar in the bowl of a stand mixer. Using the paddle attachment, cream the butter and sugar together until light and fluffy, about 3 minutes, scraping down the sides of the bowl as necessary.
Add the egg and vanilla extract and continue to mix until fully incorporated.
Reduce the mixer speed to low and add half of the dry ingredients followed by half of the buttermilk. Repeat with the remaining dry ingredients followed by the remaining buttermilk. Mix until the dough just comes together.
Reduce the speed to low and add the dry ingredients. Mix until the dough just comes together. Cover and chill the dough in the refrigerator for an hour.
Preheat the oven to 400 degrees and line a rimmed baking sheet with parchment paper. Combine the sugar and cinnamon for the topping together in a small bowl. Remove the dough from the refrigerator. Scoop tablespoons of the dough onto the prepared baking sheets leaving at least 2 inches of space between each cookie (about 12 cookies per sheet). Sprinkle the top of each cookie with the cinnamon sugar mixture.
Transfer to the oven and bake for 8-10 minutes or until the cookies are puffed and set and not brown. Remove from the oven and transfer to a wire rack to cool. Repeat with remaining dough.