Bring the quinoa and 2 cups of water to a boil in a saucepan. Cover, reduce heat to low, and simmer for 15 minutes. Remove from heat and let stand covered 5 minutes, then fluff with a fork.

In a small bowl, whisk the lime juice, olive oil, cumin, garlic powder, and salt until combined.

In a large bowl, toss the black beans, corn, tomatoes, and red onion with half of the dressing.

Divide the quinoa among bowls, top with the bean mixture, avocado slices, and cilantro, then drizzle with the remaining dressing.