In a large mixing bowl, stir together quinoa, black beans, corn, tomatoes, onion and cilantro. Squeeze lime juice over the quinoa mixture and season with spices. Stir to combine.
Cut a circle around the tops of the peppers, and using the stem, pull out the seeds. Remove any remaining seeds and white parts with your fingers.
Stuff each pepper with the quinoa mixture and transfer to a baking dish. Add a splash of water to the dish (about 1/8" high) and bake on the center rack for 40 minutes. Remove and serve immediately with avocado, sour cream and cilantro!