In a bowl combine the flour, cream of tartar, salt, and baking soda together. Set aside.
In a stand mixer with a paddle attachment, on medium-high speed, beat the butter until smooth. Add the sugars and mix until the butter starts to lighten slightly.
Add the eggs one at a time and beat until combined before adding the next one. Add the vanilla. Reduce the speed to low and add the flour mixture. Mix until just combined, place the dough into the bowl, cover in cling film, and refrigerate for at least 3 hours.
While the dough is in the refrigerator mix all of the sugar mixture ingredients together.
Preheat the oven to 350°F or gas mark 4.
Using the 2 tablespoon cookie scoop roll the dough into a ball and roll in the sugar mixture. Place on lined sheet pan. Bake for 12 minutes or until the sides start turning light brown. Allow to cool for 2 minutes before moving to a cooling rack. Repeat again once the sheet pan is cool.
Notes
This dough can be frozen in an air-tight container for up to 2 months.
If the dough is going to be frozen roll into balls first and freeze on a flat surface for a few hours before transferring to a container. This will help with baking much later.