Bring 4 cups of vegetable broth to a boil. Rinse 1 cup of quinoa under cold water, add quinoa to boiling broth, reduce heat, cover, and simmer for 12-15 minutes until fluffy.

In a skillet, heat 2 tablespoons of olive oil, add 1 chopped onion and 2 minced garlic cloves, sauté until translucent. Add 1 diced bell pepper, 1 diced zucchini, and 8 oz sliced mushrooms; cook for 5-7 minutes. Mix in 1 cup halved cherry tomatoes and 2 cups baby spinach until wilted.

Combine 1 cup tomato sauce, 1 cup Greek yogurt, and 1 teaspoon red pepper flakes in a bowl until creamy.

Preheat the oven to 190°C (375°F). Combine fluffed quinoa, sautéed vegetables, and creamy sauce in a bowl. Transfer mixture to a greased 9x13-inch baking dish.

Sprinkle 1 cup mozzarella cheese and ½ cup grated Parmesan cheese on top. Cover with aluminum foil and bake for 20 minutes, then remove foil and bake for another 10 minutes until bubbly.

Let rest for 5 minutes before garnishing with chopped parsley or basil.