For the Donuts:

• Heat the apple cider in a small saucepan over medium heat. Bring to a gentle boil and simmer for 10–20 minutes, or until reduced to approximately ½ cup. Remove from the heat and let cool.
• Preheat the oven to 350°F. Spray a donut pan with nonstick cooking spray.
• In a large bowl, whisk together the flour, baking soda, baking powder, cinnamon, nutmeg, and salt.
• In a separate bowl, whisk together the egg, brown sugar, and granulated sugar until well combined. Whisk in the melted butter, then add the reduced apple cider, milk, and vanilla extract.
• Add the wet ingredients to the dry ingredients and mix until just combined. Do not overmix. The batter will be thick.
• Pipe or spoon the batter evenly into the prepared donut pan, filling each cavity about halfway full.
• Bake for 10–11 minutes, or until a toothpick inserted into the center comes out clean.
• Let the donuts cool in the pan for 5 minutes, then transfer them to a wire rack to cool slightly.
• For the Topping:
• Combine the sugar, cinnamon, and nutmeg in a bowl.
• Once the donuts are cool enough to handle, dip each donut in the melted butter, then coat with the cinnamon sugar mixture.
• Serve warm.