Preheat your oven to 350°F (175°C).

In a medium bowl, combine the all-purpose flour, cream of tartar, baking soda, and salt. Whisk together until well blended.

In a large bowl, cream together the softened unsalted butter, granulated sugar, and brown sugar until smooth and fluffy (about 2-3 minutes).

Add the eggs to the sugar mixture one at a time, fully incorporating each before adding the next. Stir in the vanilla extract.

Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.

In a small bowl, mix together the cinnamon, red sugar, and green sugar.

Shape the dough into small balls, about one inch in diameter, and roll each ball in the sugar mixture.

Place the rolled dough onto ungreased cookie sheets, spaced apart.

Bake in the preheated oven for 10-12 minutes or until set but still soft to the touch.

Let the cookies cool on the sheet for a few minutes before transferring them to wire racks to cool completely.