Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt.

In a large mixing bowl, beat together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add in the eggs one at a time along with the vanilla extract and mix until fully incorporated.

Gradually add the dry ingredient mixture into the wet mixture and fold gently until just combined.

Gently fold in the diced Granny Smith apples until evenly distributed throughout the dough.

In a small bowl, whisk together granulated sugar, cinnamon, and nutmeg for your coating mixture.

Form small balls of dough and roll them in the cinnamon sugar mixture until well-coated, then place on prepared baking sheets.

Bake for about 8 minutes or until lightly golden around the edges but still soft in the center.

Allow them to cool on the sheets for a few minutes before transferring to wire racks.