1. preheat the oven to 375°f/190°c. 2. Whisk together the flour, cream of tartar, baking soda, and salt in a large mixing bowl and set aside. 3. Using a mixer, beat sugar and butter in a large bowl until light and fluffy. scrape the sides of the bowl with a rubber scraper as needed. 4. Add the eggs and beat until smooth and creamy, scraping the sides of the bowl with a rubber scraper as needed. 5. Mix in the vanilla. 6. With the mixer on low, gradually add the dry ingredients to the wet ingredients in three batches until just combined. the dough will be thick.