Make the coating: In a small bowl, whisk together sugar cinnamon and salt together and set aside.
For the doughnuts: Whisk together flour, baking powder, baking soda, cinnamon, nutmeg, and salt together in a bowl. In another bowl, whisk togeter apple juice concentrate, sugar, buttermilk, milted butter and egg together. Whisk half of the flour mixture into the apple juice concentrate mixture until smooth, then add the rest of the flour mixture by folding it in.
Dust a counter with flour and turn out the dough, add more flour to the top of the dough. Pat the dough into 1/3 inch thick round (10-11 inches in diameter). Cut out 3 inch rounds- with a 1 inch round removed from the center of each doughnut.
Transfer doughnuts to baking sheet with silpat. Set up a wire rack with paper towels underneath to absorb the oil.
In the dutch oven, add 1.5 inches of oil and heat to 350 degrees. Add doughnuts to oil (so they don't touch). Cook for 2 minutes flipping every 30 seconds. Watch the oil temp so it remains 325-250 degrees.
Use the spider skimmer to scoop up the cooked donuts and place on wire rack.
Lightly toss doughnuts in coating and transfer back to wire rack to cool.