Preheat your oven to 350°F (180°C) fan assist, then line 2 baking sheets with parchment paper and set aside. 

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

In the bowl of a stand mixer fitted with a paddle attachment (or using a handheld electric mixer) cream the butter and sugar on medium-high speed until light and fluffy, about 4 minutes.

With the mixer on medium speed, add the eggs, one at a time, followed by the vanilla and mix until fully incorporated.

Reduce the mixer to low speed and add the flour mixture, mixing just until just combined.

In a shallow bowl, whisk together 3 tablespoons of sugar and 1 tablespoon of cinnamon and set aside.

Using a 1 tablespoon measuring spoon, portion the dough into balls and roll each in the cinnamon sugar coating. Arrange them 1½ inch (4 cm) apart on your prepared baking sheets and chill in the fridge for 30 minutes. (Chilling helps the cookie keep its shape while baking).

Bake for 10-12 minutes or until lightly golden brown. Allow to cool on the trays for 5 minutes before transferring to a wire rack to cool completely.

Enjoy with a glass of milk! Store leftover cookies in an airtight container at room temperature for up to 3 days.