Preheat your oven to 350°F and line a baking sheet with parchment paper or silicone baking mat.
In a small bowl, stir together sugar and cinnamon. Set aside.
In a small bowl, whisk together flour, baking soda, cream of tartar, salt, and spices. Set aside.
In a medium bowl, combine melted butter, granulated sugar, and brown sugar, and whisk until well-combined. Add egg yolk, canned pumpkin, and vanilla extract and whisk until smooth.
Switch to a spoon and stir in the flour mixture until just combined. Scoop rounded spoonfuls of dough (this should make 8 cookies) and roll your dough into a ball.
Roll dough balls in the cinnamon-sugar mixture until completely covered.
Place dough on the prepared cookie sheet and use the palm of your hand to smash the dough to 1/2-inch thickness.
Bake for 10 to 13 minutes, until the cookies look set.
Allow cookies to cool on the baking sheet for 10 minutes, until cool enough to handle and transfer to a cooling rack.
Serve and enjoy!