Preheat oven to 375.
Zest 10-15 key limes as a garnish. This step is optional.
Combine all wet donut ingredients aside from ghee in a medium size bowl and whisk until well combined.
In a separate bowl, combine all dry donuts ingredients and whisk until all clumps have been removed.
Combine wet and dry ingredients and mix until well combined.
Generally grease a donut pan with ghee and using a piping bag or zip lock with a hole cut into the bottom corner, gently pipe the batter into the donut pan. The molds should be just about ¾ of the way full.
Place in the oven and bake for 10-12 minutes or until a toothpick can be inserted and comes out clean.
While the donuts are baking, combine all frosting ingredients in a small bowl and whisk to combine.
If the frosting seems too thick, add a bit of water, one teaspoon at a time.
Once the donuts have been removed from the oven and cooled, gently dip them into the frosting.
Eat right away while the frosting is soft or store in the fridge and let come to room temperature before serving.