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

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

Add egg, pure vanilla extract, and canned pumpkin puree to the mixture. Beat until smooth.

Gradually add the dry mixture to the wet, stirring gently until a sticky dough forms.

Cover the bowl with plastic wrap and refrigerate for at least 30 minutes.

Preheat your oven to 350°F. Line baking trays with parchment paper.

In a small bowl, mix granulated sugar and ground cinnamon.

Scoop and roll the dough into balls, then coat them in the cinnamon sugar mixture.

Place the dough balls on the lined trays and flatten slightly, keeping them spaced.

Bake for 8-10 minutes until edges are set. Allow to cool for 5 minutes before transferring to a wire rack.