Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a small bowl, stir together ⅓ cup granulated sugar, 1 tablespoon cinnamon, and a tiny pinch of salt. Set aside.
In a large bowl, whisk together the melted vegan butter, pumpkin purée, brown sugar, granulated sugar, vegetable oil, and vanilla extract until smooth and well combined.
In a separate bowl, whisk together the flour, baking soda, cream of tartar, salt, and pumpkin pie spice.
Gradually stir the dry mixture into the wet ingredients until a soft dough forms with no visible flour.
Scoop 1-ounce portions of dough (about 2 tablespoons) and roll into balls. Roll each ball in the cinnamon sugar mixture to coat all sides.
Place dough balls 2 inches apart on the prepared baking sheet. Gently press each one to flatten slightly with the bottom of a glass or your hand.
Bake for 10–12 minutes, until the edges are just set and the centers still look soft.
Let cookies cool on the baking sheet for 10 minutes, then transfer to a wire rack to cool completely.