Beat butter and sugars in a large bowl of stand mixer until creamy and light, about 2 minutes.
1 cup salted butter, 3/4 cup (150g) granulated sugar, 1/2 cup (100g) light brown sugar
Add pumpkin, egg, and vanilla. Beat again.
1/2 cup pumpkin puree, 1 large egg, 2 teaspoons pure vanilla extract
Add flour, cream of tartar, baking soda, salt, and 3 teaspoons pumpkin pie spice. Mix until just combined. Do not overmix. Cover with plastic wrap and chill for 30-45 minutes.
3 cups (423g) all-purpose flour, 1 1/2 teaspoons cream of tartar, 1 teaspoon baking soda, 1/2 teaspoon salt, 3 teaspoons pumpkin pie spice
Preheat the oven to 350°F. Line two baking sheets with parchment paper.
In a shallow bowl, combine granulated sugar and remaining pumpkin pie spice.
1/4 cup additional granulated sugar, 1 Tablespoon additional pumpkin pie spice
Scoop cookie dough into 1 1/2 tablespoon balls. Roll in pumpkin pie spice and sugar mixture until coated. Space 2 inches apart on prepared cookie sheets.
Bake for 10-12 minutes until set around the edges, but still soft in the middle. Cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.