Step 1

In a medium bowl, sift together flour, cream of tartar, baking soda, and salt. Set aside.

Step 2

In a mixer bowl fitted with the paddle attachment, beat butter and sugar on medium speed for 2-3 minutes, until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla extract. Add flour mixture and beat on low speed just until combined. Do not over mix.

Step 3

If the dough is soft at this point, chill in the fridge for 1-2 hours or until firm. This step results in thicker cookies that will spread less while baking.

Step 4

Preheat oven to 375F/190C. Line 2 pans with parchment paper.

Step 5

Make the cinnamon-sugar mixture: In a small bowl, toss together sugar and cinnamon.

Step 6

Shape the dough into balls, 1.5 tablespoons each (use an ice-cream scoop or heaping tablespoon), roll them in the cinnamon-sugar mixture, and place on the cookie sheet. Using your hands or the bottom of a glass, very slightly flatten each cookie, leaving them thick. Bake for about 8-10 minutes, until cookies begin to brown at the edges but the center is still soft. Cookies will appear undone but will continue to bake on the warm baking sheet. Leave cookies to cool on baking sheet for 10 minutes, then gently transfer to a wire rack to cool completely.

Step 7

Store cookies at room temperature in an airtight container for up to 3 days. Cookies can also be frozen for up to 2 months.