Rinse the quinoa under cold water.

In a medium saucepan, combine the quinoa and 2 cups of water. Bring to a boil, then reduce heat to low, cover, and let simmer for about 15 minutes or until water is absorbed and quinoa is fluffy.

While the quinoa is cooking, chop the red bell pepper and red onion. If using frozen corn, thaw it by running under water or microwaving for a few seconds.

In a large mixing bowl, combine the cooked quinoa, black beans, corn, diced red bell pepper, and red onion. Mix well to distribute the ingredients evenly.

In a small bowl, whisk together the lime juice, olive oil, cumin, salt, and pepper. Pour this dressing over the quinoa mixture and toss gently until everything is well coated.

Add fresh chopped cilantro, if using, and give it one final stir. Let it chill in the fridge for 10-15 minutes to allow the flavors to meld before serving.