Preheat a grill or grill pan on medium heat.
In a pot of boiling water cook the quinoa according to the instructions on the package. Once cooked, drain any excess water and cover with a lid to keep warm. Season with salt to taste.
Season both sides of the chicken with cajun seasoning and salt.
Heat the oil in a saucepan on medium heat. Saute the garlic and half of the amount of onion for 3 minutes. Stir in the cumin and cook for 2 minutes longer. Add the black beans, stir, and bring to a low simmer for about 8 minutes. Season with salt and pepper.
In the meantime cook the chicken on both sides to an internal temperature of 160 degrees using a thermometer. Then set aside on a cutting board to rest for 3 minutes and then dice into chunks.
In a small pan of simmering water cook the corn for 2 to 3 minutes to get it hot.
Place the quinoa in a bowl and top with chicken, black beans, tomatoes, avocado, corn, and remaining onion. Season with salt and pepper and lime juice. Garnish with cheese, lime wedges, and cilantro leaves.