Soak the lentils for a few hours or overnight.
Strain and wash.
Put the soaked lentils in a heavy cooking pot, cover with water and bring to boil.
Lower the flame and cook for 5 more minutes.
Close the flame, strain, wash and set aside.
Heat in a cooking pot the coconut oil.
Fry the onion until a little soft and transparent.
Add turmeric, cinnamon, sugar and salt.
Mix and fry for 2 more minutes.
Add the lentils, stir a bit and add the water.
Bring to boil.
Lower the flame and cook for about 10 minutes or until the lentils are soft but al dente.
Add coconut milk and curry leaves and bring to boil.
Lower the flame, cover and simmer for 15 more minutes.
If thick dahl is desired, finish cooking without the cover.