Caramelize Apples: Peel and finely dice the apples. In a pan over low-medium heat, toss with dark brown sugar, cinnamon, salt, and lemon juice. Cook for about 10 minutes until golden brown. Chill to set flavors.

Brown Butter: Melt the unsalted butter in a pot over medium heat until golden brown. Cool in the fridge for 10 minutes.

Prepare Dry Ingredients: In a bowl, whisk together flour, baking soda, cream of tartar, ground cinnamon, fine sea salt, and cornstarch.

Mix Wet Ingredients: In another bowl, whisk brown butter with dark brown sugar and granulated sugar until smooth. Add vanilla, egg, and egg yolk, blending well. Fold in caramelized apples.

Combine Ingredients: Fold dry mixture into wet ingredients until just combined. Avoid over-mixing.

Chill Dough: Cover and chill the dough for 2-3 hours.

Bake: Preheat oven to 350°F (175°C). Scoop portions, roll in cinnamon-sugar, place on a baking sheet, and bake for 12-14 minutes until edges are golden.