Rinse quinoa under cold water using a fine mesh strainer to remove its bitterness.

Cook the rinsed quinoa in 2 cups of vegetable broth for 15 minutes, then let it sit covered for 5 minutes before fluffing with a fork.

Rinse lentils well and cook in 3 cups of vegetable broth for 20-25 minutes until tender.

In a large skillet, heat olive oil and sauté chopped onion until softened, then add minced garlic.

Add spinach to the skillet, cook until it wilts, then season with cumin, paprika, salt, and black pepper.

Combine quinoa, lentils, and spinach mixture in a large bowl and adjust seasoning if necessary.

Transfer the mixture to a greased baking dish and sprinkle with optional cheese.

Preheat oven to 350°F (180°C) and bake for 25-30 minutes until golden.

Let the casserole rest for 10 minutes before serving.