Preheat the oven to 350 degrees and prepare a few cookie sheets with parchment paper.
In a large bowl or stand mixer, beat 1 cup of butter for about two minutes or until smooth, scraping the sides and bottom of the bowl a few times.
Add 1 1/3 cup of white sugar and 1/3 cup of packed brown sugar. Beat for two minutes, taking the time to scrape the bottom and sides of the bowl in between. The butter and sugar should be light and fluffy with no chunks.
Add the 2 eggs and 2 teaspoons of vanilla. Beat well, scraping the sides and bottom of the bowl. Make sure you beat it long enough that it becomes smooth and homogenous.
Place 3 1/4 cups flour in a large bowl. Add the baking soda, the kosher salt and the 1 1/2 teaspoons of cream of tartar into the flour. Mix thoroughly and then addd it gradually to the butter mixture. Continue mixing until the flour streaks are gone but don't overmix.
Use a large cookie scoop or a small ice cream scoop to shape the dough into a ball. Each ball should be 1 1/2 to 2 inches across.
In a medium bowl combine the sugar and the cinnamon thoroughly. Then roll each ball in the cinnamon sugar.
Place the cookie balls on the parchment-lined cookie sheet with about two inches between them. About 12 cookies to an average cookie sheet.
Bake the cookies at 350 for about 9 to 11 minutes, until the edges are barely set. it's OK if the centers of the cookies are still shiny. The rest of the cookie should be matte. It's very important not to overbake snickerdoodles; underbaking slightly is what gives them that soft and chewy texture.
Immediately after removing the cookies from the oven, use a spoon to push the edges of the cookies toward their centers. This makes the cookies round in shape and makes the center thicker and more chewy. You have to do this withing 30 to 60 seconds of taking them out of the oven before the edges harden.
Let the cookies sit on the pan for about 3-5 minutes. Remove the cookies to a cooling rack or on a sheet of foil.
While the cookies are still warm, but cool enough to handle, place each cookie back in the cinnamon sugar bowl. Coat one side of the cookie then flip it to coat the other. Enjoy!
26 servings