Pour the apple cider into a small saucepan and bring it to a boil. Let it simmer for about 10-12 minutes until it reduces to about 1/4 cup. This intensifies the apple flavor. Set it aside to cool.
Preheat your oven to to 350°F .
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Set aside.
In a separate large bowl, whisk together the granulated sugar, brown sugar, melted butter, egg, vanilla, reduced apple cider, and milk until well combined.
Gradually add the dry ingredients to the wet ingredients, stirring just until combined. Be careful not to overmix, as you want the donut to stay light and fluffy.
Add your dough into your donut molds. Fill 3/4 of the way.
While the donuts are cooking, mix the granulated sugar and ground cinnamon in a bowl for the coating.
