Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper. This creates a perfect non-stick surface for baking.
In a large bowl, cream together softened butter and sugar using an electric mixer or whisk until the mixture is light, fluffy, and fragrant, about 2-3 minutes.
Add the egg and vanilla extract to the creamed mixture and beat until well combined, watching for a smooth, shiny texture and a pleasant vanilla aroma.
In a separate bowl, whisk together the sifted flour, cream of tartar, baking soda, and salt until evenly mixed.
Gradually add the dry ingredients into the wet mixture, mixing on low speed until just combined. The dough should be soft but firm enough to hold shape.
In a small bowl, mix together the cinnamon and remaining granulated sugar to create the coating mixture.
Scoop out about a tablespoon of dough and roll into a smooth ball. Then, thoroughly roll each ball in the cinnamon-sugar mixture, coating evenly.
Place the coated dough balls on the prepared baking sheet, spacing them about 2 inches apart to give room for spreading.
Bake in the preheated oven for 8-10 minutes, until the edges turn golden and crackle, and the tops look set but slightly soft in the center.
Remove the cookies from the oven and let them rest on the baking sheet for 5 minutes to firm up and finish crackling.
Transfer the cookies to a wire rack to cool completely, allowing the fragrant cinnamon-sugar coating to set and develop a crisp exterior.
Enjoy your warm, crispy-on-the-outside, chewy-on-the-inside snickerdoodles! Store any leftovers in an airtight container for up to a week.
