Quinoa and sweet potato enchilada casserole

1. Make the Enchilada Sauce:
Heat olive oil in a small saucepan over medium heat. Add onion and cook, stirring occasionally, until soft, about 5 minutes. Add garlic, chili powder, cumin, and salt and cook, stirring, 30 seconds. Add tomato sauce and water. Bring to a low simmer, reduce heat, cover, and simmer for 5 minutes. Remove from heat.

2. Cook the Quinoa:
In a medium saucepan, bring 1 ½ cups water to a boil. Stir in the quinoa, reduce heat, cover, and simmer until all liquid has been absorbed, about 15 minutes. Remove from heat.

3. Cook the Sweet Potatoes:
Set a steamer basket over a pot of water and bring to a boil. Place sweet potato cubes in the steamer basket, cover, and steam until just tender, about 10 minutes. Uncover and let cool slightly.

4. Assemble the Casserole:
Preheat oven to 350 degrees F. Lightly spray a 3-quart baking dish with cooking spray.
In a large bowl, combine quinoa, sweet potatoes, black beans, enchilada sauce, 1 ½ cups of the cheese, red onion, and ¼ cup cilantro. Stir until everything is well combined. Transfer to the prepared baking dish. Top with remaining ½ cup of cheese.

5. Bake until casserole is hot and cheese is melted, about 20 minutes. Let stand for 5 minutes. Serve with additional chopped fresh cilantro and Greek yogurt or sour cream, if desired.