In a large heavy bottom pot over medium high heat, stir onions with olive oil and salt until translucent. About 5-7 minutes.
Add garlic and cook about 1 minute more until fragrant.
Add chicken breast and broth to pot and bring to a boil. Reduce to a rolling simmer, cover and let cook until chicken breast reaches an internal temperature of 165°, about 15 minutes.
Remove chicken breast from pot and shred. Add back to pot with couscous and bring to a boil again and let couscous cook, about 7 minutes.
Add lemon juice and zest to pot. Taste and add additional salt if desired. Serve hot topped with feta, chives, black pepper and optional red pepper flakes for a touch of spice!