Preheat oven to 325°F and line a baking sheet with parchment paper.
Using the paddle attachment of your stand mixer or hand mixer, cream the butter and sugar together on medium-high speed for 3-4 minutes until light and fluffy.
5 & 1/2 tbsp butter, 1/3 cup granulated sugar
Add the egg yolk and vanilla extract and mix on medium speed until everything is combined. Scrape the sides if needed.
1 egg yolk, 1/2 tsp vanilla extract
Add in the flour, baking soda, cream of tartar, cinnamon, and salt to the wet mixture and mix on low speed until just incorporated. Do not overmix.
3/4 cup all-purpose flour, 1/4 tsp baking soda, 1/4 tsp cream of tartar, 1/4 tsp cinnamon, 1/8 tsp salt
In a small bowl, mix together the sugar and cinnamon for the topping.
1.5 tbsp granulated sugar, 1/2 tsp cinnamon
Using a 2 tablespoon cookie scoop, scoop out 6 cookie dough balls. Roll them between the palms of your hands to make them smooth, then roll them in the cinnamon-sugar mixture. Place the cookies on the baking sheet, making sure to leave 3 inches between each one.
Bake for 10-11 minutes. The cookies should have spread a little with edges that are barely set and centers that still look puffy in the center and slightly soft. They will continue baking as they cool down.
Let the cookies sit on the baking sheet for 10-15 minutes, then transfer to a wire rack to cool completely.