Preheat oven to 350ºF; generously grease a nonstick 12-cup mini donut pan.
In a large bowl, whisk together almond flour, arrowroot, collagen, 2 teaspoons cinnamon, baking powder and salt. In a blender, blend cider, dates, cashew butter, ghee and vanilla until smooth. Pour cider mixture into flour mixture and stir until well combined. (Batter will be thick.) Transfer batter to a pastry bag with no tip (or a large ziplock bag; seal bag and snip off one corner). Pipe batter into donut cups in pan, filling about 2/3 full. Bake until golden and a toothpick inserted into a donut comes out clean, 11 to 13 minutes. Pop donuts out of pan onto a wire rack to cool.
Meanwhile, in a medium shallow bowl, whisk together coconut sugar with remaining 1 ½ teaspoons cinnamon and pinch of salt. When donuts have cooled, working one at a time, brush with butter, then dip in cinnamon-sugar mixture. Serve immediately. Store any leftovers covered in the fridge. (If you have leftover cinnamon-sugar, keep in an airtight container for another use.)
