Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.

In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt. Set aside.

In a large bowl, use an electric mixer to cream the softened butter and 1 1/2 cups of granulated sugar together until light and fluffy. This should take about 2-3 minutes.

Beat in the eggs, one at a time, followed by the vanilla extract, mixing until well combined.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until the dough comes together.

In a small bowl, mix together 1/4 cup of granulated sugar and the ground cinnamon.

Use a cookie scoop or spoon to form balls of dough, about 1 tablespoon in size. Roll each ball in the cinnamon-sugar mixture until well coated.

Place the coated dough balls on the prepared baking sheets, spacing them about 2 inches apart.

Bake in the preheated oven for 8-10 minutes, or until the edges are set but the centers are still soft. The cookies will puff up during baking and flatten as they cool.

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