Preheat oven to 200°C

Sift in flour, baking soda, cream of tartar (optional) and salt into a bowl. Set aside.

In a mixer, cream butter and sugar until light and fluffy. Add eggs and vanilla and mix until combined.

Add sour cream (optional) and mix until combined.

Add the flour mixture and mix at low speed until combined.

Scoop dough onto cookie sheet/s and slightly press each cookie, slightly flattening them and coating them/sprinkling them with sugar.

Bake for 10 to 12 minutes.