In a deep frying pan or large saucepan, melt the coconut oil. Finely dice the onion and garlic and add to the pan. Sauté over medium-low heat for about 10 minutes or until the onions are soft and starting to caramelize.
Peel and finely dice the potatoes and carrots, then add them to the frying pan. Allow all the veggies to cook for a further 10 minutes to allow the carrots and potatoes to soften a bit. Stir every few minutes to prevent burning.
Add the lentils, spices and tomato paste to the pan and stir so that everything gets evenly coated in spices and paste. Mix in the coconut milk and the water. Bring the Dahl up to a boil, then simmer for about 15 minutes or until the lentils are cooked. Be sure to stir often to prevent the Dahl from sticking to the pan.
In the last minute of cooking, stir in the spinach until it wilts. Serve the Dahl on its own or with rice. It can be stored in the fridge for up to five days.