In a skillet over low-medium heat, combine diced Gala apples, dark brown sugar, ground cinnamon, a pinch of fine sea salt, and a squeeze of lemon juice. Stir frequently for about 10 minutes until the apples are tender and golden brown. Once done, remove from heat and cool in the fridge.

In a medium saucepan over medium heat, melt the unsalted butter, swirling occasionally until it turns golden brown and releases a nutty aroma, about 5-7 minutes. Remove from heat and allow to cool slightly.

In a large mixing bowl, whisk together all-purpose flour, baking soda, cream of tartar, ground cinnamon, fine sea salt, and cornstarch until well combined.

In a separate bowl, whisk together the cooled brown butter, dark brown sugar, granulated sugar, and vanilla extract until smooth. Mix in the eggs, and fold in the cooled caramelized apple mixture.

Gradually add the dry ingredient mixture to the wet ingredients, folding gently until just combined. Cover the bowl with plastic wrap and chill in the refrigerator for at least 2 to 3 hours.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

Scoop out portions of cookie dough and roll them into balls about 1.5 inches in diameter. Mix granulated sugar and ground cinnamon for coating. Roll each dough ball in the sugar mixture and space them evenly on the prepared baking sheet.

Bake in the preheated oven for 12-14 minutes. The edges should be set while the tops may look slightly underbaked. Cool cookies on the baking sheet for 5 minutes before transferring to a wire rack.