Preheat oven to 400 degrees F. Coat a donut pan with nonstick spray.

In a large bowl, combine flour, baking powder, pumpkin pie spice, salt and baking soda.

In the bowl of an electric mixer fitted with the paddle attachment, beat 1/2 cup granulated sugar, brown sugar and vegetable oil on medium-high until well combined, about 1-2 minutes. Beat in eggs, one at a time, until well combined. Beat in pumpkin and vanilla until just combined. Gradually add flour mixture to sugar mixture at low speed, beating just until incorporated.

Using a piping bag fitted with a round piping tip or a large Ziplock bag with the corner cut off, pipe the batter evenly into the donut pan. Place into oven and bake for 10-12 minutes, or until donuts are slightly browned and spring back when touched.

In a medium bowl, combine remaining 1/2 cup granulated sugar and cinnamon.

When the donuts are done, cool for 10 minutes and brush the tops with butter, gently tossing in the cinnamon sugar mixture.

Serve warm or at room temperature.