Preheat oven to 400 degrees and grease a 6-count donut pan.
In a large bowl, stir flour, sugar, baking powder, salt, and spices together.
In a separate bowl, whisk together egg, buttermilk, and vanilla extract.
Make a well in the center of the dry ingredients, and add in the wet ingredients. Gently stir until just combined (batter will be very thick).
Add in sour cream, butter, and pumpkin puree. Mix until well combined.
Spoon or pipe batter into the donut pan.
Bake donuts for 10-12 minutes, or until the donuts have risen and the tops of the donuts 'spring' back when lightly touched.
Allow to cool for at least 5 minutes before removing from the tray.
In the microwave (or on the stove) melt butter and maple syrup together. Gently whisk in powdered sugar, vanilla extract, and cinnamon. Once combined, allow the glaze to cool for 8-10 minutes or so, so it can thicken.
When ready to glaze the donuts, give the glaze a quick stir, then dunk each donut about halfway into the glaze. Place donuts on a wire cooling rack to give the glaze time to set (about 10 minutes).
Enjoy!