Instructions

1. Preheat oven to 350°F. Prepare a baking sheet with either parchment paper or oil. Set aside.
2. In the bowl of stand mixer fitted with the whisk attachment, combine the softened butter, granulated sugar, and brown sugar and beat until light and fluffy, about 3 minutes. Add in the egg and egg yolk, whisking until the mixture turns slightly lighter in color. Add the greek yogurt and vanilla extract and mix until combined.
3. In a separate bowl combine the salt, baking soda, cream of tartar, and flour. Stir together the dry ingredients and then add to the wet ingredients. Mix until just combined. The mixture will be wet, but this is totally normal.
4. Combine sugar, cinnamon and salt in a small bowl. Roll 2 tablespoons of batter into a ball, then dip completely in cinnamon sugar. Place on prepared baking sheet, leaving at least 1.5 inches between each cookie. Repeat with remaining cookies.
5. Bake for 12-14 minutes, until the cookies have started to wrinkle but are still pale in color (NOT golden brown!). Remove from oven and let sit on baking sheet for 10 minutes (they will continue to cook as they cool). Enjoy with a glass of cold milk!