In a bowl mix together besan, chilli powder, 1 tsp oil, salt needed and cooking soda.
Add water and mix it nicely for 2-3 minutes.
The batter should not be too thick nor watery. It should coat the vegetables well when dipped into it. ( I added little less than 3/4 cup of water for 1 cup of besan)
Heat oil in a kadai.
Once the oil is heated, reduce the heat to medium. Now dip the thinly sliced onions in the bajji batter and drop it gently into the oil.
Fry both sides until golden brown and remove it from the oil using a slotted ladle. Keep them in a paper towel to drain off the excess oil.
Repeat the same process for the rest of the onion slices.
Recipe Notes
You can fry 4-5 bajjis at a time depending on the amount of oil you use.