Place the rinsed chana dal in a heavy-bottomed pot. Add the water and ground turmeric. Bring to a boil over medium-high heat, skimming off any foam that rises to the top.

Reduce the heat to low, cover the pot partially, and simmer gently until the dal is tender but still holds its shape, about 35-40 minutes. Stir occasionally to prevent sticking.

While the dal cooks, heat 1 tablespoon of coconut oil in a separate pan over medium heat. Add the diced onion and sauté until soft and translucent, about 5 minutes. Add the garlic and ginger, cooking for 1 minute until fragrant. Add the diced tomatoes and cook until they break down and become jammy, about 4-5 minutes.

Once the dal is tender, stir in the onion-tomato mixture, salt, and the full-fat coconut milk. Simmer the mixture together uncovered for 5-10 minutes to allow the flavors to meld and the dal to thicken slightly. Remove from heat.

To make the tadka, heat 2 tablespoons of coconut oil in a small skillet over medium-high heat. Add the black mustard seeds. As soon as they begin to pop, lower the heat slightly and add the cumin seeds, dried red chilies, asafoetida (if using), and fresh curry leaves.

Fry the spices and curry leaves for 30-45 seconds until the curry leaves are crispy and fragrant. Immediately pour the hot oil and spices over the cooked dal. Stir gently to incorporate.