In a medium bowl, sift together the flour, baking soda, salt, cornstarch, and cream of tartar. Set aside.
Beat together room temperature butter and brown sugar on medium for 2 minutes. It will become light and fluffy. Add in vanilla. Scrape the bowl. Add in peanut butter and mix until well combined. Scrape the bowl.
Add in eggs one at a time on low. Slowly add in dry ingredients and mix until well combined. Place bowl in fridge to chill for 1- 1 ½ hours This will help firm up the dough and prevent spreading.
Preheat oven at 350°F. Prepare 2 cookie sheets with parchment paper or silicone baking sheets.
Mix sugar and cinnamon together in a small bowl. Use a 1 ½ tablespoon cookie scoop and scoop up the cookie dough. Don't round out the ball, we want to keep the beautiful ripples intact. Roll the cookie dough ball in cinnamon sugar. Place cookie dough 2 inches apart.
Bake for 10-13 minutes. The cookies are done when the edges are set and the bottom is golden brown. Let cookies sit on cookie sheet for 10 minutes before transferring to cooling rack.