Bring the apple cider to a boil. Then lower heat to medium and simmer until reduced to 1/3 cup, about 15-18 minutes. Remove from heat and cool to room temperature.
Preheat oven to 350F. Grease two 6-well donut trays.
Whisk together all the dry ingredients in a bowl.
In another bowl whisk together all the wet ingredients. Pour in the cider and whisk that in.
Add the dry ingredients to the wet ingredients. Using a silicone spatula, mix together the wet and dry with a few swift strokes.
Spoon the batter into a large resealable bag, making sure the batter is spooned to the bottom of the bag. Press out the air and seal the bag. Snip about a 3/4 inch piece off one bottom corner.
Pipe the batter into the wells of the trays, filling each a little past halfway.
Bake for 9-11 minutes or until they are firm to the touch.
Turn then out onto a cooling rack while you make the topping.
Heat the butter until it melts. Mix together the sugar, cinnamon, and nutmeg in a bowl large enough to fit the donuts.
Brush some butter on a donut, then roll it around in the sugar pressing a bit to adhere the topping. Repeat for each.