In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice.
In a large bowl, whisk together the egg, vanilla extract, vegetable oil, kefir, sugars, and pumpkin puree.
Gently fold the dry ingredients into the wet ones just until the flour streaks disappear.
Transfer the batter into a piping bag, cut off the tip, and pipe batter evenly into the greased donut pan so that it's about level with the pan's center hole.
Bake the donuts on the middle rack for about 10 minutes. Test if they're done by gently poking a donut - if it springs back up, it's ready to come out of the oven!
Let the donuts cool in the pan for about 10 minutes, then transfer them to a cooling rack.
Optional (wait until you're ready to serve them): Mix together the cinnamon and sugar in a small/medium bowl. Working one at a time, lightly brush melted butter over each donut and then dunk them in the cinnamon-sugar mixture.
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Notes
Quantity: The number of donuts this recipe yields may differ by donut pan size.Storage: Store cooled, uncoated donuts in an airtight container at room temperature for 4 days or in the freezer for 2 months. Thaw at room temperature and apply the melted butter/cinnamon sugar coating before serving.Kefir: This recipe is sponsored by my friends at Lifeway Foods. Their organic whole milk plain kefir is best in this recipe, but can be substituted with buttermilk if needed.