1. Chop tomatoes to medium-sized pieces.
2. Boil tomatoes and tamarind together for 8-10 mins in water.
3. Allow it to cool, and squeeze the complete tamarind and tomato juice mixture by adding required amount of water.
4. Heat 2 tbsp oil in a kadai, add dry chillies, followed by garlic, cumin and pepper powder followed by curry leaves.
5. Fry for a few minutes, and then add the squeezed juice to the boiling mixture.
6. Add required amount of salt, and bring it to a boil.
7. Finally garnish with coriander.

Note: The best indication to stop is when you observe light foam on the rasam.