Grease the cake pan generously with oil.
Add the besan, jaggery powder, turmeric powder, lemon juice, green chili paste, garlic ginger paste, oil, asafoetida and salt into a bowl. Whisk in the water until smooth.
The batter should easily flow off a spoon. If it's too thin, add in a tablespoon of besan.
Bring water to a boil over high heat in a wide pot, filled about halfway. Once the water is boiling, quickly whisk the baking soda into the besan mixture, let it bubble and pour it into the greased pan.
Place the cake dish in the pot of boiling water. Let it cook for 20 minutes, then lower the heat to medium, cover with a lid fully and cook for another 25 minutes. After this time, check if a toothpick inserted in the center comes out clean. If not, continue to cook for a few more minutes.
Once it's cooked, turn off the heat. Use a butter knife along the edges of the pan to loosen it up. Place a clean plate on top of the cake pan, then using oven mitts, invert the pan onto the plate. It should easily come out upside down.