Lightly oil 9 donut pan holes with coconut oil.
In a large mixing bowl, stir together the melted butter, coconut sugar, maple syrup, vanilla extract, and salt. Add the baking soda, cream of tartar, and eggs. Stir until all the ingredients are combined.
Add the cassava flour, tapioca flour coconut flour, and coconut milk. Stir until combined. Chop the frozen strawberries and gently fold them into the batter.
Spoon the dough into the donut pan holes. Fill each hole until the batter is level with the raised center of the hole. Gently smooth the batter in each hole. Chill in the refrigerator for 20 minutes.
While the donuts are chilling, preheat the oven to 350 degrees F. After the donuts have chilled, bake them for 10-12 minutes. The donuts should spring back when you gently press them. Allow the donuts to set in the pans for 3 minutes, then remove the donuts to a cooling rack.
While the donuts cool, make the marshmallow fluff frosting. In a medium mixing bowl, sprinkle the gelatin over the water. In a small saucepan, heat the honey, vanilla, and salt over medium heat, stirring periodically.
Once the honey mixture has begun to simmer, continue to stir constantly until the mixture reaches a temperature of 240 degrees F. Then, slowly pour the honey mixture into the gelatin while beating at a medium speed with beaters.
Continue to beat the mixture at a high speed for 4-5 minutes. The mixture should double in volume and become thick and sticky. Spread the marshmallow fluff frosting over the donuts.
Decorate and enjoy!