01 - Preheat your oven to 375°F (190°C).
02 - In a medium saucepan, combine the rinsed quinoa with the vegetable broth. Bring the mixture to a rolling boil, then reduce the heat to low, cover tightly, and simmer for 15 minutes, or until all the liquid has been absorbed. Remove from heat, fluff the grains with a fork, and set aside.
03 - While the quinoa is cooking, heat the olive oil in a large skillet over medium heat. Add the finely diced onion and sauté until it becomes translucent, approximately 3 minutes. Introduce the minced garlic, diced zucchini, and quartered cherry tomatoes. Continue to cook for another 5 minutes until the vegetables begin to soften.
04 - Stir in the chopped fresh spinach and cook until it has wilted down, which should take about 2 minutes.
05 - Remove the skillet from the heat. Add the cooked quinoa, half of the shredded cheese (if using), dried oregano, smoked paprika, ground cumin, salt, and black pepper. Mix all ingredients thoroughly to ensure an even distribution of flavors.
06 - Arrange the hollowed bell peppers upright in a lightly greased baking dish. Carefully spoon the prepared quinoa and vegetable mixture into each pepper cavity, pressing gently to pack them snugly.
07 - Evenly distribute the remaining shredded cheese over the top of each stuffed pepper. Cover the baking dish tightly with aluminum foil.
08 - Place the covered baking dish in the preheated oven and bake for 25 minutes. Following this, remove the aluminum foil and continue to bake for an additional 10 minutes, or until the bell peppers are tender and the cheese on top is melted and golden brown.
09 - Remove the dish from the oven. Garnish the stuffed peppers with freshly chopped parsley. Serve immediately with optional lemon wedges on the side.