Rinse the squid briefly and pat it very dry with paper towels. Excess moisture will prevent the masala from roasting properly.

Heat 1 tablespoon coconut oil in a large skillet over medium heat. Add the mustard seeds and cover briefly; let them pop for about 30 seconds.

Add half the curry leaves, the onions, and green chilies. Cook for 10–12 minutes, stirring frequently, until the onions are soft and deep golden brown.

Stir in the ginger and garlic. Cook for 1 minute, until fragrant.

Reduce the heat to medium-low. Add the turmeric, chili powder, cayenne, coriander, black pepper, fennel, and garam masala. Stir for 30 seconds. Add the tomato and salt, then cook for 5–7 minutes, until the tomato breaks down and the mixture becomes thick and glossy. Add up to 2 tablespoons water if the spices begin sticking.

Increase the heat to medium-high and add the squid. Stir well to coat it with the masala. Cook uncovered for 4–6 minutes, stirring occasionally, until the squid is just opaque and tender and any released liquid has mostly evaporated. Avoid overcooking, which can make squid rubbery.

Add the remaining tablespoon of coconut oil and curry leaves. Stir-fry for another 2–3 minutes, until the masala is dark, concentrated, and clings to the squid.

Stir in the lime juice. Taste and adjust the salt, pepper, and cayenne. Serve hot with steamed rice, Kerala parotta, appam, or chapati.