Place the quinoa and water in a medium saucepan. Bring to a boil. Reduce heat to low and simmer, covered, for about 15 minutes or until water is absorbed and quinoa is soft. Drain excess water.
While the quinoa cooks, prepare the dressing by whisking all dressing ingredients together.
Place drained tuna and quinoa in a medium bowl and stir to combine. Add dressing and stir well to combine. Season with salt and pepper to taste.
Serve in cabbage cups, lettuce cups, over spinach, or anyway you prefer. Top with chopped green onions and additional lime juice.