Preheat and prep: Heat your oven to 400°F (200°C).
Slice the tops off the bell peppers and remove seeds and membranes. If needed, trim the bottoms slightly so they stand upright without tipping.
Cook the quinoa: Rinse 1/2 cup quinoa under cold water. Add to a saucepan with 1 cup broth.
Bring to a boil, reduce heat, cover, and simmer for 15 minutes, or until fluffy. Set aside.
Soften the veggies: Warm olive oil in a skillet over medium heat. Sauté onion for 3–4 minutes until translucent.
Add garlic and cook 30 seconds, just until fragrant.
Add zucchini and tomatoes: Stir in zucchini and cherry tomatoes. Cook 4–5 minutes until tender and the tomatoes start to break down slightly.
Season the filling: Mix in tomato paste, cumin, smoked paprika, oregano, salt, and pepper. Cook 1 minute to bloom the spices.
Combine with beans and quinoa: Fold in the beans and cooked quinoa.
Taste and adjust salt, pepper, or spices. Stir in fresh parsley or cilantro.
Fill the peppers: Arrange peppers upright in a baking dish. Spoon the filling into each pepper, packing gently.
If using cheese, sprinkle lightly on top.
Bake: Add a splash of water (about 1/4 cup) to the bottom of the dish to create steam. Cover loosely with foil and bake 20 minutes. Uncover and bake another 10–15 minutes, until peppers are tender and tops are lightly golden.
Finish and serve: Let cool for a few minutes.
Squeeze a little lemon over the top for brightness. Serve warm.