Begin by preheating your oven to 350°F (175°C). Line two baking sheets with parchment paper to prevent sticking and ensure even baking.
In a medium bowl, combine the all-purpose flour, baking soda, cream of tartar, and salt. Whisk together until well blended, then set this mixture aside.
In a large mixing bowl, add the softened butter, granulated sugar, and brown sugar. Using a hand mixer or stand mixer, cream these ingredients together on medium speed for about 2-3 minutes, until the mixture is light and fluffy.
Crack the eggs into the mixing bowl one at a time, blending well after each addition to ensure they are fully incorporated. Next, pour in the vanilla extract and mix until combined.
Gradually add the dry flour mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to over-mix, as this could result in a tougher cookie.
In a small bowl, combine the 2 tablespoons of granulated sugar with the ground cinnamon, stirring until evenly mixed.
Using a cookie scoop or a tablespoon, scoop out portions of dough, roughly 1 1/2 inches in diameter, and roll them gently into balls between your palms.
Roll each dough ball in the cinnamon-sugar mixture, making sure they are fully coated for that signature Snickerdoodle flavor.
Place the cinnamon-sugar coated dough balls on the prepared baking sheets, ensuring they are spaced about 2 inches apart to allow for spreading during baking.
Bake the cookies in your preheated oven for 10-12 minutes. You want the edges to turn a light golden color while the centers remain soft and slightly underbaked for the best texture.
Once done, remove the cookies from the oven and let them sit on the baking sheets for 5 minutes. This allows them to firm up a bit before transferring them to a wire rack to cool completely.
Notes
Arrange several cookies in a charming stack on a decorative plate. Pair with a refreshing glass of milk.