In a large mixing bowl, whisk together the flour, cream of tartar, baking soda, ground cinnamon and salt until well combined. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using an electric mixer, beat the butter, granulated sugar, and brown sugar together for about 1-2 minutes or until well combined. Mix in the egg, egg yolk, and vanilla extract until well combined, stopping to scrape down the sides of the bowl as needed.
Add the dry ingredients and mix until just combined. Cover tightly and refrigerate for at least 1 hour.
Preheat oven to 350°F (177°C). Line large baking sheets with parchment paper or silicone baking mats and set aside.
Remove the cookie dough from the refrigerator. Using a 1 tablespoon cookie scoop or measuring tablespoon, scoop the cookie dough onto the prepared baking sheets. Each ball of cookie dough should measure about 1 and 1/4 inches once you roll it into a ball.
In a small mixing bowl, whisk together the 1/4 cup of sugar and 2 teaspoons ground cinnamon for the coating. Roll each ball of cookie dough into a ball, then coat in the cinnamon sugar mixture and place back on the baking sheets, making sure to leave a little room between each one.
Bake for 8-10 minutes or until the tops of the cookies are set. Remove from the oven and allow to cool on the baking sheet for 5-10 minutes, then transfer the cookies to a wire rack to cool completely.