Combine melted butter, sugar, and brown sugar; stir until well-combined. Add pumpkin and stir well.

Stir in egg yolk and vanilla extract.

In a separate bowl, whisk together flour, pumpkin spice, baking soda, cream of tartar, and salt until well-combined.

Gradually add dry ingredients to wet mixture until well-combined.

Cover cookie dough with clear wrap and place in the refrigerator to chill for at least 45 minutes.

Preheat oven to 350?F (175?C) and line a cookie sheet with parchment paper. In a small bowl, whisk together ? cup sugar and 2 teaspoons ground cinnamon for the topping.

Remove dough from refrigerator, scoop into 1 ? Tablespoon-sized balls, roll smoothly, and coat with cinnamon sugar. Transfer to prepared cookie sheet, spacing at least 2 inches apart.

Bake cookies in the preheated oven for 10-12 minutes. Keep remaining dough refrigerated while baking.

Allow baked cookies to cool completely on the cookie sheet before enjoying.