Line a baking sheet with parchment paper or a silicone mat.
Make the Cinnamon-Sugar Coating by mixing the granulated sugar and cinnamon for the cinnamon sugar in a shallow dish. Set aside.
Mix dry ingredients; all-purpose flour, baking soda, cream of tartar, cinnamon and salt. Set aside.
In a large bowl, beat soft butter with sugar until fluffy and light, about 2 minutes.
Add the egg and mix until fully incorporated.
Add in the flour mixture on low speed until just combined. Make sure all the flour is incorporated.
Use a teaspoon and portion out the cookie dough into 2 teaspoon sized small balls. Roll the dough in the palm of your hand and then roll them through the cinnamon-sugar to coat.
Place the cookie balls on baking sheet, about 2 inches apart. (NOTE 1)
Bake cookies in oven for 7-9 minutes. The cookies will just start to wrinkle. Allow them to cool on the baking sheet (this way they will bake a few more minutes). (NOTE 2) and then cool completely on a wire rack.
Notes
This recipe makes about 30 small snickerdoodles and they did not fit all on one large baking sheet, so I used a second half-sized baking sheet to accommodate all of them. Of course, when you roll the balls a little larger, you may get away with one baking sheet.
Snickerdoodles can become dry easily by baking them too long. These cookies are smaller than usual, so their cooking time is even shorter.