Make the batter, mix all of the dry ingredients in a mixing bowl with water to create a batter with a consistency similar to heavy cream (double cream in the UK). You might need to add more water than written in the ingredient list above.
Slice the onions into thin slices and separate them just a little.
Add the onions to the batter.
Stir the onions with the batter so that it coats the onion slices well.
Heat canola or vegetable/corn oil to 355°F (180C°), then using 2 spoons of your hands start dropping clusters of onions in the batter (about 3-4 at a time), and fry for 3-4 minutes or until golden brown and crispy.
Using a spider or slotted spoon, remove the bhajis from the oil, and place on a plate lined with paper towels. Enjoy hot on their own, or serve with a yogurt mint raita.