Rinse the lentils and place them in a large crockpot. Add the diced onions, garlic, ginger, coconut oil, curry paste, garam masala, turmeric, sugar, and cayenne. Stir to combine.
Pour just 1 can of tomato puree over the lentils. Re-fill the can with water twice and add to the crockpot. Stir to make sure that the lentils are covered with liquid. Cover and cook on high for 4-5 hours or low for 7-8 hours.
Check once or twice during cooking to add more water or tomato puree if the lentils are soaking up all the liquid. The amount of water or tomato puree you add depends on how soupy your want your lentils to be. For me, 1½ cans of tomato puree plus the two cans of water was perfect. Taste and season with salt. Lentils will be soft when they are done cooking.
Stir in the coconut milk and sprinkle with cilantro just before serving.
Vegan/Vegetarian/GF/DF
This recipe adapted and taken from Pinchofyum.com.