Combine lemon juice, onions, chilies, and black pepper to make a marinade. Place chicken in a single layer in a baking dish or other glass container, and cover with the marinade. Seal the dish with plastic wrap and and refrigerate for about 30 minutes or longer. Remove chicken from marinade and grill until crisp and brown, basting with marinade. Remove from grill. To complete the dish, simmer the grilled chicken in the marinade for about 15 minutes. Serve the yassa over white boiled rice, topping with the cooked marinade.