Heat a light colored skillet or pan over medium heat. Add the butter and melt. Whisk continuously as the butter begins to bubble. Watch for the butter to start to brown and remove from heat. I like to add the butter to my mixing bowl so it can cool quicker.
While the butter is cooling add the pumpkin to a paper towel lined plate. Let sit for 10 minutes to absorb moisture while gathering remaining ingredients. Use additional paper towels to blot the pumpkin dry as possible. This is essential for getting a chewy cookie and not cake like texture.
Once the butter is cooled to room temperature, add both types of sugar and cream together using either a hand or stand mixer. Add the egg, pumpkin puree and vanilla and mix until combined.
In a separate large bowl add the flour, spices, baking soda, cream of tartar and salt. Whisk to combine.
Slowly add the flour ingredients to the wet ingredients. Mix until combined and no white streaks of flour remain. Use a spatula if needed to scrape the sides and bottom of the bowl. Be cautious to not over mix.
Cover the bowl and place the cookie dough in the refrigerator to chill for at least 30-45 minutes.
Preheat oven to 350℉. Line a cookie sheet with parchment paper.
Use a 340 cookie scoop or about 1.6 tablespoons of dough to make cookie dough balls. Place in cinnamon sugar to coat. Place dough balls on the parchment paper spacing a couple inches apart.
Bake in preheated oven for 11-12 minutes. When cookies come out of oven use the bottom of a flat glass to lightly press the cookies down to give that flatter snickerdoodle appearance.
Sprinkle with additional cinnamon sugar and cool on a wire rack before transferring to an airtight container. These cookies can be stored at room temperature for 3-4 days (if they last that long)!