Preheat oven to 350°F. Line 2 12-count cupcake tins with cupcake liners (this recipe makes 18 cupcakes). Set aside.
In a large bowl, mix the vegetable oil, brown sugar, granulated sugar, eggs, and vanilla together just until combined.
½ cup vegetable oil, ½ cup brown sugar, ¼ cup granulated sugar, 2 large eggs, 2 teaspoons pure vanilla extract
Add the pumpkin puree to the wet ingredients and mix to combine. Set aside.
1½ cups pumpkin puree
In a separate medium bowl, whisk together the flour, pumpkin pie spice, cinnamon, baking powder, baking soda, and salt.
1⅓ cups all-purpose flour, ½ tablespoon pumpkin pie spice, 1 teaspoon ground cinnamon, 1 teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon kosher salt
Add the dry ingredients to the wet ingredients and mix just until combined. Scrape down the sides of bowl.
Lightly beat in the buttermilk.
2 tablespoons buttermilk
Fill the wells of each cupcake tin about ¾ full of cupcake batter.
Bake for 20-22 minutes or until toothpick inserted in middle comes out clean.
Cool completely before frosting.