Reduce to a simmer and add the chicken. Season, cover and cook for about an hour.
Peel and cut the plantains into 1-inch thick chunks and add to the pan after the chicken has cooked for 30 minutes. Cover and cook for 5-7 minutes till plantains are cooked but not mushy. Take off the lid and simmer for a few more minutes till the gravy is slightly thicker. Then add the tomatoes a few minutes before serving, garnish with cilantro and serve with white rice.
Notes
Adapted from The Brazilian Kitchen by Leticia Shwartz