Using a mortar and pestle, coarsely crush cumin seeds, black pepper, and garlic. Keep aside.
Heat oil in a pan and add cumin seeds.
Add sliced onion and broken dry red chillies. Saute until the onion turns translucent and the raw smell disappears.
Add cleaned murungai keerai leaves and saute for about 5 minutes until the leaves are cooked and wilted.
Pour in 1 cup of water and add the coarsely crushed spice mixture along with salt.
Bring the soup to a rolling boil and simmer briefly.
Switch off the heat and serve hot.