1. Preheat the oven to 350 degrees Fahrenheit. Prepare several baking sheets with parchment paper or silicone baking mats.

2. In a large bowl or stand mixer, beat the softened salted butter for 2 minutes until smooth and creamy. Scrape the sides and bottom of the bowl as needed.

3. Add 1 and 1/3 cups granulated sugar and 1/3 cup packed brown sugar. Beat for 2 minutes until the mixture is light, fluffy, and fully combined.

4. Add the eggs and vanilla extract. Beat well, scraping the bowl to make sure the mixture becomes smooth and homogenous.

5. Add the all-purpose flour to the bowl, but do not mix yet.

6. Using a small spoon, stir the baking soda, kosher salt, and cream of tartar into the flour so the dry ingredients are evenly distributed.

7. Mix the dry ingredients into the butter mixture gently. Stop mixing when a few flour streaks remain, then scrape down the bowl with a spatula.

8. Beat just a few more seconds until the flour disappears. Do not overmix, or the cookies may turn tough.

9. Use a large cookie scoop or spoon to shape the dough into balls about 1 and 1/2 to 2 inches across.

10. In a small or medium bowl, stir together 1/3 cup granulated sugar and 1 and 1/2 tablespoons cinnamon.

11. Roll each dough ball in the cinnamon sugar until fully coated, reserving the remaining cinnamon sugar for after baking.

12. Place the dough balls on the prepared baking sheets, leaving about 2 inches between each cookie.

13. Bake for 9 to 11 minutes, until the edges are barely set and the centers are still slightly shiny. Do not overbake.

14. Immediately after removing the cookies from the oven, use a spoon to gently push the edges of each cookie toward the center to make them more round and thick in the middle.

15. Let the cookies rest on the baking sheet for 3 to 5 minutes.

16. While the cookies are still warm but firm enough to handle, return each cookie to the cinnamon sugar bowl and coat both sides for extra flavor.

17. Transfer to a wire rack to cool slightly, then serve warm or at room temperature.