Preheat the oven to 350°F (180ºC). Heat the apple cider in a small saucepan over medium-high heat. Simmer and reduce the cider to ½ cup.
In a large bowl, whisk together the flour, brown sugar, 1 tablespoon of the cinnamon, baking soda, salt and baking powder.
In another large bowl, beat together 2 tablespoons of butter and the eggs until combined. Whisk in ½ cup of the reduced cider and buttermilk.
Stir the wet ingredients in to the dry until just combined.
Lightly grease a donut pan with vegetable oil cooking spray. Spoon the batter into the donut pan until each mold is ¾ full.
Bake for 10 minutes, until when you stick a knife in the donut, the knife is clean.
In a small shallow bowl, melt the remaining 6 tablespoons of butter. In another shallow bowl, stir together granulated sugar and the other tablespoon of cinnamon.
Dip both sides of each donut into the butter and then the cinnamon sugar mixture.
Serve warm or room temperature on a platter and store leftovers in a tightly sealed container.