Peel and finely dice the Gala apples. Toss them in a skillet with dark brown sugar, ground cinnamon, a pinch of salt, and lemon juice. Cook on low-medium heat for about 10 minutes until browned and tender. Let chill.

Melt unsalted butter over medium heat, stirring until it becomes a deep golden brown, about 6-8 minutes. Allow to cool for approximately 10 minutes.

In a medium bowl, whisk together all-purpose flour, baking soda, cream of tartar, ground cinnamon, cornstarch, and a pinch of salt. Set aside.

In a large bowl, combine chilled brown butter with dark brown sugar, granulated sugar, and vanilla. Whisk until smooth. Add in the egg and yolk, followed by the cooled apple mixture. Gently fold together.

Gradually fold dry ingredients into wet mixture until just combined. Cover with plastic wrap and refrigerate for 2-3 hours.

Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper. Mix granulated sugar with cinnamon for coating.

Use a cookie scoop to form the chilled dough into 1 tablespoon balls. Roll in cinnamon sugar and place 2-3 inches apart on the baking sheet.

Bake for 12-14 minutes until edges are golden brown and tops look slightly underdone. Cool on the baking sheet for 5 minutes before transferring to a wire rack.