Mash roughly chopped tomatoes with your hands in a bowl and keep aside. You can add little water while mashing if you need.
Soak tamarind in ½ cup hot water for 20 mins and extract its juice, keep aside.
In a pan, dry roast horse gram, coriander seeds and red chilli in medium flame, until the horse gram turns golden red in colour. Take care not to burn it. Just roast until golden in colour and fragrant.
Grind it along with pepper, jeera and curry leaves, to a powder in a mixer.
Heat oil/ ghee in kadai, temper with mustard. Sprinkle asafotida and put the flame to low. Add the ground powder, turmeric powder and crushed garlic.
Give it a fry and add the mashed tomato.
Add tamarind extract, salt and enough water and boil for 5 minutes. Switch off the flame. Garnish with chopped coriander leaves.