Combine quinoa and water in a pot. Cover and simmer for 15 minutes, until all liquid is absorbed.
While quinoa is cooking wash tomatoes, onion, bell pepper, and cilantro and cut tomatoes in halves, slice onion and pepper, cut avocado into chunks, and chop cilantro.
Cool quinoa in the refrigerator. When cooled, gently mix in vegetables and all other remaining ingredients.