Wash the greens and drain the leaves. Roughly chop it. In a pressure cooker, take the greens, chopped onions, chopped tomatoes, red chili powder, turmeric powder, tamarind, slit green chillies, 1/2 cup water. Pressure cook for 3 whistles.
Once the pressure falls, stain away excess water, using a churner, churn it well to a smooth mix. Add the water back, along with salt, simmer till it becomes thick.
Now, heat cooking oil in a pan, add mustard seeds, crushed garlic, urad dal, cumin seeds, curry leaves and fry till golden. Pour this over the simmering dal.
Serve with rice.