Preheat oven to 325 degrees F (165 degrees C). Line 2 baking sheets with parchment paper and grease paper with butter.
Whisk flour, baking powder, baking soda, cinnamon, and salt together in a bowl.
Beat white sugar and eggs together in the bowl of a stand mixer fitted with a paddle attachment on medium speed until smooth and color lightens, about 1 minute. Scrape down the sides of the bowl and paddle with a rubber spatula. Add pumpkin, oil, and vanilla and beat on low until blended.
Beat flour mixture into pumpkin mixture on low until flour is just incorporated. Mix butterscotch chips into dough.
Drop 1/4-cup scoops of dough 2 1/2 inches apart onto the prepared baking sheets. Slightly flatten the tops of the dough with a spatula.
Bake the cookies in batches in the preheated oven until tops feel firm and a toothpick inserted into the center of a cookie comes out clean, about 15 minutes. Cool on the baking sheets for 5 minutes before transferring cookies to wire racks to cool completely. Dust cooled cookies with confectioners' sugar.
