If the chana dal is unroasted, heat some oil in a small pan on medium heat. Once hot, add the chana dal and roast until it's golden brown. Strain out the oil and add it to the blender.
Cut the coconut meat into smaller chunks and add it to the blender. Grind the coconut and chana dal together. Add a bit of water and scrape down any bits and pieces as needed to get the blender going.
Then, add the serrano peppers, ginger, salt, curry leaves, and lemon juice. Continue to run the blender, adding water from the top until the blender runs smooth. Transfer the chutney to a bowl.
Heat a tadka pan with on low to medium heat. Add the mustard seeds and red chili. Cook until the mustard seeds start to pop, then add the asafoetida and curry leaves. Once the curry leaves turn crisp, remove the tadka from heat.
Pour the tadka on top of the coconut chutney.
Mix the chutney together with a spoon. Serve with dosa, idli, etc.