In a saucepan, add the chopped tomatoes, green chilies, grated ginger, minced garlic, turmeric powder, and black pepper powder.
Add 2 cups of water to the saucepan and bring it to a boil. Let it simmer for about 10-12 minutes until the tomatoes are soft and well-cooked.
In the meantime, prepare the tempering. In a skillet or tadka pan, heat oil over medium heat.
Add black mustard seeds and let them splutter. Add cumin seeds and curry leaves and sauté for 1 minute.
Pour the tempering into the simmering tomato mixture and mix well.
Add tamarind pulp and salt to taste. Let it simmer for another 5-7 minutes to allow the flavors to blend.
Garnish with chopped coriander leaves and serve hot as a soup or with rice.