Peel and finely chop the apples, then toss them with brown sugar, cinnamon, salt, and lemon juice until evenly coated. Cook the mixture over low to medium heat until the apples soften and caramelize, about 10 minutes, then chill completely in the refrigerator. prep

Place the butter in a saucepan over medium heat and melt fully, stirring occasionally as it sizzles and bubbles. Continue cooking until the foam settles and golden bits form, then transfer the browned butter to a new container and refrigerate briefly to cool. prep

In a bowl, whisk together the flour, baking soda, cream of tartar, cinnamon, salt, and cornstarch until evenly combined. Set aside. mix

In a separate bowl, whisk the cooled browned butter with both sugars and vanilla until smooth, then add the egg and egg yolk and mix until fully incorporated. Gently fold in the chilled caramelized apples. mix

Add the dry ingredients to the wet mixture and fold gently just until a dough forms. Cover tightly and refrigerate for 2 to 3 hours. assemble

Once chilled, heat the oven to 350°F and line a baking sheet with parchment paper. Stir together the sugar and cinnamon for the coating in a small bowl. prep

Scoop portions of dough, roll them generously in the cinnamon sugar, and place them spaced apart on the prepared baking sheet. assemble

Bake until the edges are lightly golden and the centers remain soft and puffy, about 12 to 14 minutes. bake

Allow the cookies to cool briefly on the pan before transferring to a rack, or enjoy while still warm. finish