Preheat the oven to 325 degrees F (165 degrees C). Line 2 baking sheets with parchment paper; grease paper with butter.

Whisk flour, baking powder, baking soda, cinnamon, and salt together in a bowl. Set aside.

Beat white sugar and eggs together in the bowl of a stand mixer fitted with the paddle attachment until smooth and creamy. Scrape down the sides of the bowl and paddle with a rubber spatula. Beat in pumpkin purée, oil, and vanilla extract on low speed until blended.

Beat flour mixture into pumpkin mixture on low speed until just incorporated: fold in butterscotch chips.

Drop 1/4 cupfuls of dough 2 1/2 inches apart onto the prepared baking sheets: slightly flatten dough tops with a spatula.

Bake in the preheated oven until edges are golden, about 15 minutes. Cool on baking sheets briefly before transferring cookies to a wire rack to cool completely. Sprinkle cookies with confectioners' sugar.