Preheat oven to 400 degrees F.
In a large Dutch oven, stir together tomatoes, onion, garlic, ginger, salt, garam masala, brown sugar, cumin, and diced chicken.
Cover the pot and bake for 30 minutes. Stir, and check to make sure that the chicken is cooked through.
Once chicken is done, stir in the coconut milk.
Garnish with cilantro just before serving. Serve over rice, if desired.
