Preheat your oven to 350°F. Prepare baking sheets by lining them with parchment paper.

In a medium-sized mixing bowl, whisk together the flour, cornstarch, baking soda, salt, nutmeg, and cinnamon until well combined. Set this mixture aside.

Using a hand or stand mixer, cream the softened butter until smooth and creamy. Gradually mix in both the brown sugar and granulated sugar, ensuring they are fully blended.

Incorporate the eggs one at a time into the creamed mixture, mixing thoroughly after each addition. Periodically scrape down the sides of the bowl to ensure even blending.

Gradually add the prepared dry ingredients to the wet mixture, mixing well after each addition. Once fully combined, stir in the diced apples by hand. The dough will be thick, so mix carefully until the apples are evenly distributed.

In a small bowl, combine the cinnamon and sugar for the coating.

Scoop out a heaping tablespoon of the cookie dough, then roll it in the cinnamon sugar mixture until evenly coated. Place the coated dough onto the prepared cookie sheet and gently flatten it slightly.

Bake the cookies for 8 minutes, then rotate the baking sheet and continue baking for another 8 minutes. Bake one sheet at a time to ensure even cooking.

Remove the cookies from the oven and allow them to cool slightly on the baking sheet before transferring them to a wire rack to cool completely.