Combine the dry ingredients: In a medium mixing bowl, start assembling the cookie dough. Whisk together the flour, cream of tartar, pumpkin pie spice, baking soda, and salt.
2
Chill: Cover the bowl and chill the dough in the refrigerator for at least 30 minutes. The dough can be stored in the refrigerator for up to 3 days. Chilling the dough makes it easier to scoop and shape and improves the flavor and texture of the cookies.
3
Combine the wet ingredients: In a large mixing bowl, whisk together the melted butter, pumpkin purée, brown sugar, granulated sugar, egg yolk, and vanilla extract until fully combined and smooth.
4
Make the batter: Fold the dry ingredients into the wet ingredients with a wide rubber spatula until just incorporated and no dry streaks of flour remain. At this point, the dough will seem soft.
