In a large bowl, whisk together the flour, baking soda, cream of tartar, 1 1/2 teaspoons of cinnamon, nutmeg, and salt. Set aside.

In a stand mixer fitted with the paddle attachment, beat the softened butter and 1 1/2 cups of granulated sugar together on medium speed for about 2 minutes until smooth and creamy.

Add the blotted pumpkin puree, egg yolk, and vanilla extract to the butter mixture. Beat on medium-high speed until fully combined and smooth.

Gradually add the dry ingredients to the wet ingredients on low speed, mixing just until the flour disappears. Do not overmix.

Cover the bowl with plastic wrap and chill the cookie dough in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper.

In a small bowl, mix together the 1/4 cup of granulated sugar and 1 tablespoon of cinnamon for the coating.

Scoop the chilled dough into balls, approximately 1.5 tablespoons each, and roll them thoroughly in the cinnamon-sugar mixture.

Place the coated dough balls on the prepared baking sheets about 2 inches apart, gently pressing down on the tops to flatten them slightly.

Bake for 11 to 13 minutes, or until the edges are set and the centers are still soft. Transfer to a wire rack to cool slightly before serving warm.