In a medium saucepan, bring 3 cups of apple cider to a boil.

Continue boiling until the cider is reduced to about 1 cup. This concentrates the flavor.

Remove from heat and let it cool completely.

In a mixing bowl, whisk the cooled cider, eggs, and melted butter together until well combined.

In a separate large bowl, whisk together the flour, brown sugar, baking powder, salt, baking soda, nutmeg, allspice, and cinnamon.

Gradually pour the wet mixture into the dry ingredients.

Use a spatula or your hands to mix until a sticky dough forms.

Cover the bowl and chill the dough in the refrigerator for at least 1 hour to make it easier to handle.

Turn the chilled dough out onto a well-floured surface.

Roll it out to a ½-inch thickness.

Use a floured donut cutter or round cookie cutters to cut out donuts and holes.

Fill a heavy-bottomed pot or deep fryer with 3 inches of oil.

Heat the oil to 350°F (175°C), monitoring the temperature with a cooking thermometer.

Carefully lower the donuts into the hot oil, frying in batches to avoid overcrowding.

Fry for 2-3 minutes on each side, or until they are golden brown and cooked through.

Use a slotted spoon to transfer the donuts to a paper towel-lined plate to drain excess oil.

While the donuts are still warm, roll them in cinnamon sugar to coat them evenly.

Enjoy the apple cider donuts warm, savoring the rich apple flavor and spices.