Add the buckwheat groats, brown rice, quinoa, salt, and water to a medium saucepan. Bring to a boil, then lower the heat and cook covered for about 20 minutes, or until the grains are soft. Drain excess water if needed and set the cooked grains aside.

Heat the oil in a large skillet over medium heat. Once hot, add the onion and garlic and cook for 3-5 minutes, or until the onions are soft. Add the mushrooms and cook for another 5 minutes, stirring regularly.

Next, add the diced tomatoes with their juice, cooked black beans, nutritional yeast, apple cider vinegar, chili powder, oregano, salt, and ground cumin. Cook for another 5 minutes. Add the cooked grains and stir well until everything is coated with the sauce. Taste and adjust seasonings if needed, adding more chili for spiciness or a drizzle of maple syrup if you like it sweeter. Remove from heat and set aside.

Preheat the oven to 350°F (175°C).

Cut a top off the zucchinis to make a "hat". Using an ice cream scoop, scoop out the pulp. Save the pulp for other uses (it's great in veggie stir-fries).

Place the zucchinis in a large baking dish, or iron skillet. Pour about 1/2 cup of water in the bottom of the dish, this prevents the zucchini from sticking to the bottom.

Fill each zucchini with the enchilada preparation and top with the "hats". Drizzle with olive oil and bake for 45-50 minutes, or until the zucchinis are soft.

Serve immediately and top with parsley, red pepper flakes, and a squeeze of lime juice. These stuffed zucchinis can be served with a salad on the side.

Stuffed zucchinis are best served the same day but will keep for up to 4 days in the refrigerator. To reheat, cover the baking dish with aluminum foil and place in a 350°F preheated oven for 30 minutes.