In a large sauté pan with a lid, or a dutch oven, add a tablespoon of olive oil, and heat over medium high heat. Add sliced onions and peppers and sauté for 5-7 minutes, until tender and beginning to brown. Remove from pan and set aside.
To the same pan, add the quinoa, crushed tomatoes, vegetable broth, salt, spices, beans, and corn. Stir to combine, and then allow to come to a boil over medium high heat.
Once the pot is boiling, reduce heat to low, and cover. Simmer for another 30-40 minutes, until most of the liquid is absorbed. Be sure to check, because the tomato sauce will rise to the top.
Once your rice is cooked, stir the tomato sauce back into the quinoa, and top with shredded cheese, if desired. Place the lid back on top and let it sit for a couple of minutes until the cheese is melted.
Top the dish with sautéed peppers and onions, avocado, tomatoes, cilantro and green onion, or any other toppings you desire!