In a large bowl, combine the sliced onions, red chili powder, grated ginger, chopped cilantro, green chili (if using), cumin, and turmeric.
Toss everything together until the onions are well-coated in the spices.
Sprinkle the chickpea flour over the onion mixture but do not mix yet.
Let it sit for about 10 minutes.
Add the salt to the bowl. Now, using your hands, mix and mash the flour and salt into the onions for 3-5 minutes. This process is key, as the salt will draw out moisture from the onions, creating a thick, sticky batter without needing any water.
Pour about 1. 5 cm / 1/2 inch of oil into a heavy-bottomed frying pan or wok and heat over a medium flame. The oil is ready when a tiny piece of the mixture dropped in sizzles and rises to the top immediately.
Working quickly, take small portions of the onion mixture and form them into 12 rough, rustic patties.
Don't worry about stray pieces of onion sticking out – these will become wonderfully crispy.
Carefully place half of the bhajis into the hot oil, ensuring not to overcrowd the pan.
Fry for about 1-2 minutes per side, then continue to turn them occasionally for another minute or two until they are a deep reddish-gold and crisp all over.
Remove the cooked bhajis with a slotted spoon and let them drain on a wire rack or a plate lined with paper towels.
Repeat the frying process with the remaining mixture.
Serve immediately while piping hot with green chutney or tamarind chutney for dipping.
Do not add any water to the batter. Massaging the salt into the onions is the secret to drawing out the perfect amount of natural moisture to bind the fritters.
Fry in batches to avoid overcrowding the pan. This keeps the oil temperature from dropping and ensures each bhaji has space to become golden and crisp.