Preheat the oven to 375°F (190°C).
Place the bell peppers upright in a baking dish.
In a medium saucepan, bring the vegetable broth to a boil.
Add the rinsed quinoa to the boiling broth, reduce heat to low, cover, and simmer for 15 minutes or until the quinoa is tender and liquid is absorbed.
While the quinoa cooks, heat olive oil in a skillet over medium heat.
Add the chopped onion and cook for 3-4 minutes until translucent.
Add the minced garlic and cook for another 1 minute until fragrant.
Stir in the diced zucchini and cook for 5 minutes until slightly softened.
Add the cherry tomatoes, black beans, ground cumin, smoked paprika, salt, and black pepper. Cook for 3 more minutes, stirring occasionally.
Remove the skillet from heat and stir in the cooked quinoa and chopped cilantro.
Spoon the quinoa mixture evenly into each bell pepper, filling them completely.
Sprinkle the shredded cheddar cheese evenly over the stuffed peppers.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10 minutes until the cheese is melted and slightly golden.
Remove from the oven and let cool for 5 minutes before serving.