In a saucepan over medium heat, boil the apple cider until it reduces to about 1/2 cup, approximately 15-20 minutes. Let it cool slightly.

Melt the unsalted butter in a skillet over medium heat, stirring until it turns golden brown and smells nutty, about 5-7 minutes.

In a large bowl, mix the brown butter, granulated sugar, brown sugar, egg, vanilla extract, and reduced apple cider until well incorporated.

In another bowl, whisk together the all-purpose flour, baking powder, baking soda, cinnamon, nutmeg, and salt.

Gradually add the dry mixture to the wet mixture, stirring until just combined. Be careful not to over-mix!

Preheat your oven to 350°F (175°C) and lightly grease your donut pan.

Fill each donut cavity about 2/3 full using a piping bag or zip-top bag with a corner snipped off.

Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean.

Let the donuts cool in the pan for a few minutes before transferring to wire racks to cool completely.

In a small bowl, mix the granulated sugar and cinnamon for coating. Roll the cooled donuts in the cinnamon-sugar mixture.