Combine the sugar and cinnamon in a small, shallow bowl. Set aside while you make the cookies.
To make the cookies:
Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone liners.
Whisk together the flour, baking soda, cinnamon, cream of tartar and salt. Set aside.
Using an electric mixer on medium speed, beat the butter, sugar and brown sugar until light and fluffy. Add the eggs, one at a time, mixing well after each addition. Mix in the vanilla.
Reduce mixer speed to low. Gradually add the flour mixture, mixing just until combined.
Using a tablespoon of dough at a time, roll the cookies into balls and then roll each in cinnamon- sugar. Place the cookies on the prepared pans, leaving about 2 inches between cookies.
Bake, one pan at a time, 8 to 10 minutes, or until the cookies are lightly browned and appear set.
Place the pans on a wire rack and allow to cool for 10 minutes. Then, transfer the cookies from the pan onto a wire rack to cool completely.
Notes
To store. Store snickerdoodles in an airtight container at room temperature for up to 5 days. I don't recommend storing them in the fridge, as they might become hard.
To freeze. Snickerdoodles freeze well and can be stored for up to 3 months. Simply place them in a freezer bag or airtight container and thaw them at room temperature before enjoying. You can also freeze the dough for later use by rolling it into individual balls and placing them on a lined baking sheet in the freezer until frozen, then transferring them to a freezer bag or container. When ready to enjoy, simply bake the frozen dough balls at the same temperature for a few extra minutes.