In a medium saucepan, bring 2 cups of vegetable broth to a rolling boil. Rinse 1 cup of quinoa under cold water to remove any bitterness, then add it to the boiling broth. Reduce the heat to low, cover the saucepan, and let it simmer for 12-15 minutes, or until the liquid is absorbed and the quinoa is fluffy. Fluff the quinoa with a fork and set it aside.

Heat 1 tablespoon of olive oil in a large skillet over medium heat. Once the oil is shimmering, add the diced onion and minced garlic, sautéing for about 2 minutes until fragrant and translucent.

To the skillet, add the chopped bell pepper, zucchini, mushrooms, and halved cherry tomatoes. Cook for 5-7 minutes, stirring frequently until they soften and release their juices.

Toss in the fresh baby spinach along with the dried oregano, dried basil, smoked paprika, salt, and pepper. Stir until the spinach wilts, about 1-2 minutes.

In a small bowl, mix together 1 cup of tomato sauce, 1/2 cup of Greek yogurt, and a pinch of red pepper flakes for heat. Stir until well combined and creamy.

Preheat your oven to 190°C (375°F). In a large mixing bowl, combine the cooked quinoa, sautéed vegetables, and prepared sauce. Gently fold until evenly coated, then transfer to a greased baking dish.

Sprinkle a layer of mozzarella and Parmesan cheese over the top. Cover with aluminum foil and bake for 20 minutes.

After 20 minutes, remove the foil and bake uncovered for an additional 10 minutes, until the cheese is golden and bubbly.

Let the casserole rest for about 5 minutes before serving. Garnish with freshly chopped parsley or basil.