Peel and thinly slice the onions. Separate the onions.
Add the besan, rice flour, green chilli, and spices to a bowl and mix well.
Add water and mix well.
Then add the onions and mix really well to coat the slices - you can mix with your hands or a fork. Let this sit for at least 10 minutes (you can heat the oil during this time - see next step). As it sits, the onions will release their own water, then mix well again.
Heat oil in a deep, wide-bottomed pot such as a dutch oven, over medium high to high heat. Once the oil reaches 360°F, or when a small drop of the mixture sizzles and floats to the top, the oil is ready.
Use your hands to carefully drop some batter into the oil (try to keep the onions together when you drop the batter in - you don’t want it to spread), wait for a minute or until slightly firm and golden, then flip the pakora and wait another minute to cook the other side. (The temperature of the oil will fluctuate and is best when within the 360 to 380 range).
Remove from the oil using a slotted spoon, and place on a paper towel to absorb any remaining oil.