In a pan, add gingelly oil, splutter mustard, followed by little fenugreek seeds and curry leaves.
Add onions and saute it for about 2-3 minutes.
Add garlic. Saute onions and garlic together till both gets done for about 10 min.
When its ¾ done, add a tbsp of all purpose chilli powder (kuzhambu milagai thool), ¼ tsp of turmeric powder and salt as required.
Saute it for about 7-10 min and add a tsp of thick tamarind paste.
Add half a cup of water and check consistency.
Increase or decrease water level based on your consistency preferences. Close it and let it get done.
Switch off when its starts to boil and let it stand for some time with lid closed.
Serve with rice.