Season chicken with salt and cayenne.
Heat covered sauté pan over medium heat. Coat the pan lightly with non-stick cooking spray and cook chicken breasts until done (internal temperature of 165º). Remove from heat and cover with aluminum foil.
Add onion to the pan and cook until translucent, 3-4 minutes.
Add quinoa, chicken broth, and lime zest. Stir to combine and bring to a boil.
Reduce heat to low, cover, and simmer 15-20 minutes. Remove from heat.
Slice chicken breasts.
Add lime juice and cilantro to quinoa and fluff with a fork. Top with chicken breasts.