In a vessel take tamarind, chopped tomatoes, salt, turmeric powder and pepper powder.
Boil at slow flame till tomatoes are cooked.

Add some water. Adjust salt as required. Now prepare for tempering.
Heat pan with oil. Splutter fenugreek seeds, mustard seeds.

Add cumin seeds, pounded garlic, dry red chillies and curry leaves.

Add grated ginger and a dash of hing.

Now strain and put the boiled rasam water. Mash the tomatoes and tamarind so that the pulp gets incorporated. Add rasam powder. Boil it at medium flame.
As it boils nicely and you get a nice aroma, switch the flame off. Garnish with coriander leaves.

If you like it little sweeter add a small piece of jaggery and mix till it dissolves. But I don't add it.
Serve hot with hot rice and any spicy curry...