Begin by rinsing the lentils (dal), then placing them in a medium-sized pan, with enough water to cover. Bring to the boil, reduce the heat, put a lid on the pan, and allow the lentils to simmer until they’re soft, and have absorbed the water.
While the lentils are cooking, heat the coconut oil in a large skillet, wok, or kadai over a high heat.
Add the cumin seeds, and allow to splutter for 30 seconds or so.
Add the onion, and sauté for 2-3 minutes.
Add the garlic, stir well, and continue to fry for another five minutes or so, until the raw smell has gone.
Lower the heat slightly, and stir in the turmeric, salt, chilli powder, and green chilli, and give everything a thorough stir.
Mix in the ground coriander and garam masala, plus the chopped tomato, and stir-fry for 2-3 minutes.
Add the cooked lentils, and gently mix in well, taking care not to break up the lentils too much.
Add the water (if using).
Stir-fry for another 30 seconds or so, then add the chopped coriander.
Stir-fry for another minute, and then serve.
Leftovers can be kept in the 'fridge in an airtight container for up to three days.
You can also use yellow lentils or urad dal (black lentils... although they're white once the skins have been removed). I don't recommend puy lentils though because they tend to be too firm.