Salute the onion in a little water until it begins to soften and turns brown. Add the ginger, garlic and saute for a further two minutes.
Add the lentils, tomato, turmeric and stir together for two minutes.
Pour in enough cold water to cover the ingredients and fill until there's five cm/ two inches of water above the ingredients. Bring to the boil, then turn down and simmer for 25-30 minutes, or until the lentils are soft. Keep checking to ensure the lentils aren't sticking to the bottom of the pot or that all the water has evaporated. If this is the case just add some water from the kettle.
Once the lentils are cooked, blend them until smooth. Add your choice of vegetables (if you're using spinach add just a couple of minutes before serving) and more water if needed. Cook for a further five minutes then add the tamarind, dhansak masala and fenugreek.
Taste, then adjust the seasoning adding a little salt if you want, more tamarind and then add the fresh coriander leaves. Stir then serve into warm plates with the brown rice.