Set oven to broil on high. Cut eggplant in half and place flat-sides down on a lightly oiled baking sheet. Grease the skin of the eggplant with a little oil, poke a few holes (so it doesn't burst) and place in the oven. Keep checking it until the outer skin starts cracking and can be easily peeled. You want the skin to burn a little so the eggplant has a smoky flavor.
Allow the eggplant to cool a little. Peel the outer skin of the eggplant under cold water. When the skin is removed, mash the eggplant well so that it has an even consistency, you can keep seeds or remove them based on your preference.
Put oil in a pan. When hot, add asafetida (or onion powder) and cumin. After a minute when the cumin gives off aroma, add the finely chopped onions. When the onions are light golden brown, add the finely cut green chilies and ginger. Heat the mixture for 2-3 minutes. Then add tomatoes and stir until the sauce is pulpy and separates from the oil. Add the garam masala and eggplant to the mixture. Combine and crush the eggplant as much as possible, until the eggplant is well blended into the onion and tomato paste mixture.
Serve immediately, or simmer on low for a bit to enhance the flavor.
When ready to eat, garnish with cilantro and serve warm with naan or roti (Indian flat bread).