In a food processor, combine the onions, the 1/2 cup cilantro, 1/2 cup parsley and 2 tablespoons of the lemon juice. Add the cumin, ginger and turmeric.
Season with 1 tsp salt and process to a pulpy puree. Transfer to a large resealable plastic bag. Add the garlic and 3 tablespoons of the oil.
Add the chicken pieces, seal the bag and massage to coat the chicken with the mixture. Refrigerate for at least 8 hours or up to 24 hours.
In a large pot, warm 1 tablespoon of the oil over medium-high heat. Add the lemon slices and sear until browned, 3 to 5 minutes. Transfer to a plate.
Add the remaining 2 tablespoons of oil to the pot. Remove the chicken pieces from the marinade, shaking off the excess and reserving the marinade.
Working in batches, sear the chicken pieces, skin side down, until golden brown, 5 to 6 minutes. Transfer to another plate.
Pour the broth into the pot, stirring to scrape up any browned bits from the pot bottom. Stir in the reserved marinade and add the chicken and any juices.
Bring to a boil, cover, reduce the heat to medium-low and simmer until the chicken is opaque throughout, about 40 minutes.
Simmer the olives in a saucepan of boiling water for 5 minutes. Add the olives, the reserved lemon and the remaining 2 tablespoons of lemon juice to the pot.
Cover and simmer until the chicken is falling-off-the-bone tender, 10 to 15 minutes. Garnish the stew with chopped cilantro and parsley and serve.
