Preheat the oven to 350F and arrange a steam basket into a small saucepan filled with an inch of water on the stove top. Bring the water to a boil, then cover and steam the 1 1/2 cups of sweet potatoes for about 10 minutes, or until fork-tender. Remove from the heat and set aside.
To prepare the filling, melt the coconut oil in a large skillet over medium heat and saute the chopped onion and garlic for about 5 minutes, until tender. Add in the drained black beans, cumin and salt, and saute for another 2 minutes until well mixed. Transfer the steamed sweet potatoes to the pan, and use the back of a spoon or fork to mash all of the filling ingredients together. I prefer a slightly chunky texture to the filling, but you can leave it as smooth or chunky as you like!
To prepare the zucchini wrappers, all you need is a good vegetable peeler or a mandoline. (I used a mandoline to create uniform slices.) Carefully slice the zucchini into thin, long slices. You'll need about 5 slices to create each enchilada wrap, so 20-25 uniform slices should be enough to fill an 8"x8" glass dish. Once you've created enough zucchini slices, arrange 5 of them on a cutting board, slightly overlapping each slice over the other.
Scoop a generous portion of the enchilada filling along the zucchini slices (as pictured above) then gently roll up the zucchini over the filling to create each enchilada. Repeat the process 3-4 more times, until you have enough rolls to fill your baking dish.
To prepare the enchilada sauce, simply combine all of the ingredients in a high-speed blender and blend until completely smooth. Adjust the flavor to taste, if necessary.
Pour a bit of the enchilada sauce into the bottom of your glass baking dish, to prevent sticking. Arrange the enchilada rolls on top of the sauce, then pour the rest of the sauce over the top of the enchiladas.
Place in the preheated oven to bake for 30 minutes at 350F.
The finished enchiladas will be tender and piping hot! Serve immediately, with a garnish of diced green onions, if desired.