Pour 1½ cups apple cider into a small saucepan and simmer until reduced to ½ cup. Let cool.
Preheat oven to 350°F and grease a donut pan.
Whisk together all dry ingredients.
In another bowl, whisk together all wet ingredients.
Add the wet ingredients and cooled cider to the dry ingredients and mix until just combined. Don’t overmix!
Pipe the batter into your donut pan, filling each cavity about ¾ full.
Bake for about 10–12 minutes, or until the donuts spring back when lightly pressed.
Let them cool for a couple minutes, then brush with melted butter and toss in cinnamon sugar.
