Place the tomatoes and tamarind in about 4-5 cups of water and either cook on a low flame for about an hour or pressure cook for 15 minutes. The tomatoes should be totally mushy. Mash or grind the pulp and pass it through a sieve to extract the juice, set aside.
In a pressure cooker, heat the oil and fry the ginger garlic paste for a few seconds. Add in the meat, spice powders and salt. Add a cup of water and pressure cook for about 15-20 minutes until the meat is tender.
Add in the tomato juice into the meat mixture. Adjust the consistency with water and season to taste. Add in a green chili or two if desired. Put in the handful of chopped herbs and simmer covered for a few minutes until the oil floats on top.