Preheat oven to 375°F and line a baking sheet with parchment paper or a silicone baking mat. Spray with non-stick spray.
In a medium bowl, combine flour, cream of tartar, baking soda, and salt.
In a large bowl, beat softened butter with both sugars until smooth and creamy.
Add in 1 egg and beat until just combined. Add in the egg yolk and vanilla extract and beat until combined. Scrape down the sides of the bowl as needed.
Add dry ingredients to the wet ingredients in 3 additions, mix until just combined after each. Once all of the dry ingredients are added, mix until smooth and no flour pockets remain.
In a small bowl, whisk together the cinnamon and sugar.
Roll the dough into 2-3 tablespoon-sized balls and coat with the cinnamon sugar. Place on the prepared baking pan 3" apart and bake for 8 minutes.
Allow the cookies to cool on the pan for 10 minutes before transferring to a plate or a wire rack. Cookies stay fresh in an airtight container at room temperature for 1 week.