In a medium pot, combine water, quinoa, cumin, cayenne, garlic and salt. Bring to a boil. Reduce to a simmer and continue cooking, covered, for 15 minutes.
For the Pico de Gallo: In a medium bowl, combine all ingredients. Set aside.
In a large bowl, combine quinoa, black beans, corn and pico de gallo. Divide into serving bowls and top with cheese, lettuce, avocado and sour cream.