Heat oil in a large soup pot over high heat. Add onion and salt and sautéuntil limp, about 3 minutes. Add all spices and sauté until they release their fragrance, about 2 minutes. Add tomato paste and sauté for another minute, until darkened but not burned. (If tomato paste looks too dark too quickly, lower heat.).
Add celery, turnip and sweet potato and continue to sauté until celery starts to soften, about 10 minutes.
Return heat to high (if you lowered it), and add broth to pot. Bring to a simmer, then add chicken. Partially cover pot, lower heat to medium low and simmer for 15 minutes.
Add chickpeas and cilantro to pot and continue simmering until chicken is cooked through and vegetables are tender, about 10 minutes longer. Stir in the lemon juice and more salt if desired.
Garnish with chopped cilantro and lemon wedge and serve.