In a bowl mix together besan, rice flour, baking powder, salt and red chilly powder.
Add water little by little until you have a thick smooth batter.
Slice onions into long thin slices.
Add it to the batter and mix well.
Meanwhile heat oil in a kadai.
Drop spoon full of batter into oil.
Fry four to five bajjis at a time depending on the size of the pan.
Flip the bajjis and fry them until golden.
Serve them hot with ketchup.