In a medium saucepan, heat apple cider to boiling, then simmer for about 10 to minutes to reduce to half
Remove from heat and let cool completely.
In a large bowl, combine flour, brown sugar, baking soda, salt, cinnamon, nutmeg and all-spice. Set aside
In a separate bowl, whisk together cooled apple cider, eggs and cooled butter.
Pour wet ingredients into dry ingredients and mix together until a sticky dough forms and all the flour has been incorporated.
Cover and refrigerate 1-½ hours or overnight.
Place 3 to 4 inches of oil in a large heavy pot and heat to 325°F.
Remove from the fridge and working with ¼ of the dough at a time, roll out on a clean floured surface to ½” thickness.
Cut into doughnuts using a floured doughnut cutter.
Once oil is heated, place 3 or 4 doughnuts in the oil and fry 2-3 minutes per side
Remove from oil and place on a cooling rack over a baking pan or paper towel lined pan.
Cool slightly before coating in cinnamon sugar.
Repeat with remaining doughnuts.
Serve warm