Have ready cookie sheets and line with parchment if needed.
In a saucepan over medium heat, melt ¾ cup unsalted butter, stirring constantly. Continue cooking until it foams and brown bits form at the bottom, about 5–7 minutes.
Remove from heat and let cool slightly, about 15 minutes. Remove excess foam from the surface.
In a bowl, beat the browned butter with ⅔ cup white sugar and ⅔ cup light brown sugar until well combined.
Add 1 egg, 1 egg yolk, and 1 ½ teaspoons vanilla extract. Mix until smooth; the mixture will be shiny.
In a medium bowl, sift together the dry ingredients: 2 cups all-purpose flour, ½ teaspoon baking soda, 1 teaspoon cream of tartar, 1 teaspoon cornstarch, ½ teaspoon salt and 1 teaspoon ground cinnamon.
Add to the wet mixture in 2 parts, and stir until just combined. Don’t overmix.
In a shallow, small bowl, combine ⅓ cup sugar and ¾ teaspoon ground cinnamon.
Scoop cookie dough, 1 to 2 tablespoons pieces, roll quickly into balls between your hands (they might be slightly irregular, that is fine), and roll to coat in the cinnamon sugar.
Place in the prepared baking sheets, leaving about 1-inch of space between them, and refrigerate the cookie balls for 1 hour.
Preheat oven to 350°F (175°C).
Bake for 10-12 minutes, until edges are set, top is cracked, and centers look slightly underdone for chewy cookies, and 2-3 more minutes for crispier cookies. The time will vary depending on the size of your cookies.
Let cool on the sheet for 5 minutes before transferring to a wire rack to cool completely. They will crisp quickly as they cool, so you might prefer to put them in jars if not eating immediately.