Heat the oil in a large skillet over medium-low heat. Add the onion and cook, stirring occasionally, for 7 minutes. Sprinkle with the curry powder and cook, stirring, for 1 minute. Add the yogurt and cream and simmer gently for 3 minutes. Stir in the salt, pepper, and tomatoes (if using). Remove from heat.
Slice or shred the chicken, discarding the skin and bones. Divide the rice (if using) and chicken among individual bowls, spoon the sauce over the top, and sprinkle with the cilantro.