In a medium bowl, whisk together the flour, cream of tartar, pumpkin pie spice, cinnamon, baking soda, and salt. Set aside for now.
In a larger mixing bowl, beat the butter for one minute until light and fluffy. Add sugar and brown sugar and beat another minute, until fully incorporated and fluffy again.
Add the egg yolk and vanilla and mix, then pumpkin and mix well, scraping down the sides occaisionally.
Gently stir in the flour mixture until just combined. Cover with saran wrap and chill for half an hour.
When dough is chilled, preheat the oven to 375°F. Mix the sugar coating ingredients in a shallow bowl. Line a cookie sheet with parchment paper.
Make 1-inch balls of dough, then roll in the sugar mixture to coat fully. Place on the cookie sheet with about 2 inches of space between. Using the bottom of a glass or other flat clean surface, gently press the cookies to be about ½ inch thick.
Bake for 8-10 minutes, then let the cookies cool an additional three minutes on the cookie sheet before moving to a cooling rack to finish cooling.