Wash and soak the lentils for an hour, drain well.
Peel, halve and finely chop the onion.
Blend the tomatoes.
Puree the garlic cloves and ginger.
Trim the green chillies, deseed and blend.
In a pan add the water, drained lentils, rapeseed oil, half the butter, 2g turmeric, and 1g salt.
Bring to the boil and cook until the lentils have softened, for approximately 45 minutes to an hour.
For the tadka, add the ghee to a pan on medium heat, add the cumin seeds, sizzle for a minute.
Add the asafoetida and green chilli paste, cook for 1 minute, then add the red onion, allow to soften and slightly colour.
Add the ginger and garlic pastes, cook for another minute.
Add the remaining turmeric, chilli powder, ground cumin and remaining salt, mix well.
Add the blended tomatoes and butter, lower the heat, and cook with the lid on for 5 minutes so the masala can split.
Remove from the heat and set aside.
Once the lentils are cooked, transfer to the tadka, mix well, bring slowly back to the boil.
Chop the coriander.
Add the chopped coriander and garam masala, cook for a final 2 minutes, then remove and serve.
