Wash and soak horse gram overnight in cold water. You can soak horse gram in boiling hot water for just 30 mins too..
Take the drained horse gram in a pressure cooker. Cover with water and pressure cook till done.
If you are soaking it overnight, then pressure cook it for 3 whistle,simmer for 10 mins. Turn off the heat and let the pressure go all by itself.
if you are soaking it in hot water for 30 mins, then pressure cook it for 5 whistle, simmer for 15 mins, turn off the heat and let the pressure go all by itself.
Once the horsegram is cooked, drain it. Reserve the liquid. You can use the cooked horsegram to make sundal.
Take garlic and cumin in a blender and make it into a coarse mix.
Heat oil in a sauce pan, add in the crushed garlic and cumin seeds. Saute for a min,
Add in tomatoes and green chillies. Saute for 5 min or so.
Now add in chilli and turmeric powder along with salt and sugar. Mix well.
Add in tamarind pulp and the cooking water of horse gram. Add more water if needed.
Mix everything really well and bring it to boil. once it starts to boil, turn off the heat and add in fresh coriander leaves and mix well.
Now make the seasoning, by heating oil and add in all the seasoning ingredients. Let it sizzle for a min. Pour this over the rasam and mix well.