In a saucepan, combine lentils, ginger, garlic, chilli, celery, fresh coriander, lemon juice, water, tamarind, green onions and carrot. Bring to a boil, reduce heat and simmer partly covered 40 minutes or until lentils are soft.
Blend the lentils and vegetables until smooth then return to the saucepan.
In a small frypan, combine the garam masala, turmeric, ground coriander and cumin seeds. Cook over medium heat about 2 minutes until fragrant.
Add the spices to the dhal and stir well. Heat through and serve.