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

Cream the Butter and Sugar: In the bowl of a stand mixer fitted with the paddle attachment (or a large bowl using a hand mixer), beat the softened butter and the 1 ½ cups of granulated sugar together on medium speed until light and fluffy, usually about 3 to 4 minutes. Scrape down the sides of the bowl as needed.

Add Eggs and Vanilla: Reduce the mixer 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.

Combine Wet and Dry Mixtures: Gradually add the dry ingredient mixture to the wet mixture, mixing on low speed until just combined. Be careful not to overmix the dough once the flour is added. The dough will be soft.

Chill the Dough (Recommended): For best results and easier handling, cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 30 minutes, or up to 2 hours. This helps the cookies maintain their shape during baking.

Preheat and Prepare the Coating: Preheat your oven to 375°F (190°C). Line two large baking sheets with parchment paper or silicone baking mats. In a small, shallow bowl, combine the ½ cup of granulated sugar and the 2 tablespoons of ground cinnamon for the coating.

Shape and Coat the Cookies: Scoop the cookie dough using a 1.5-tablespoon cookie scoop (or roll into 1-inch balls). Roll each dough ball thoroughly in the cinnamon-sugar mixture until completely covered.

Bake the Cookies: Place the coated dough balls on the prepared baking sheets, ensuring they are spaced about 2 inches apart. Bake one sheet at a time for 8 to 11 minutes. The edges should be set, but the centers should still look soft and slightly puffy. For maximum chewiness, remove them when the centers are still very soft.

Cool and Serve: Let the cookies cool on the baking sheet for 5 minutes before carefully transferring them to a wire rack to cool completely. Store the cooled cookies in an airtight container at room temperature for up to one week.