Prepare the Dry Ingredients: In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt. Set this mixture aside.

Cream the Butter and Sugar: In the bowl of a stand mixer fitted with the paddle attachment, cream the softened butter and 1 ½ cups of granulated sugar together on medium-high speed. Beat for 3 to 4 minutes until the mixture is light, pale, and fluffy; this aeration is crucial for a chewy texture.

Add Eggs and Vanilla: Reduce the speed to low. Beat in the eggs one at a time, ensuring each egg is fully incorporated before adding the next. Stir in the vanilla extract. Scrape down the sides of the bowl as needed.

Combine Wet and Dry: With the mixer set to low speed, gradually add the reserved dry ingredients to the wet mixture. Mix only until just combined; do not overmix the dough.

Preheat Oven and Prepare Coating: Preheat your oven to 375°F (190°C). Line two large baking sheets with parchment paper. In a shallow, separate bowl, combine the ¼ cup of granulated sugar and 2 tablespoons of ground cinnamon for the coating.

Scoop and Roll: Use a 1.5-tablespoon cookie scoop to portion the dough. Roll each piece of dough gently between your palms to form a smooth ball.

Coat and Arrange: Drop the dough ball into the cinnamon sugar mixture. Roll until it is completely and generously coated on all sides. Place the coated dough balls onto the prepared baking sheets, ensuring they are spaced about 2 inches apart.

Bake: Bake for 8 to 10 minutes. The edges should look set, but the centers should still look slightly soft and puffy. For the chewiest result, do not overbake.

Cool: Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes (they are very delicate when hot). Carefully transfer the cookies to a wire rack to cool completely.