Cut the chicken into small pieces. Heat the oil and fry the finely chopped onions, garlic and ginger. When they begin to turn color, add the spices and cook for a few minutes longer. Add the tomatoes and salt to taste and cook for a further 5 minutes. Put in the chicken pieces and stir so that they are thoroughly coated with the sauce. Cover and simmer for about 30 minutes.
At the end of this time the mixture should be almost dry, but you need to check from time to time and add a little water if necessary.