Preheat the oven to 200 C / Gas 6. Line a large baking tray with baking parchment.
Gently sweat the onions off in a frying pan with some oil until they turn translucent, about 6-8 minutes.
Sprinkle in the chilli powder and mix. Add the turmeric, cumin, ginger, coriander and stir well. Remove from the heat.
Place the chickpea flour, salt, coriander, cumin into a medium bowl and mix well. Add the onions and tomato puree into a bowl and mix. Add a little bit of water to get the correct consistency, it should be wet and easy to stir, but not sloppy.
Drizzle some oil onto the prepared tray, place 2 tablespoons of the onion mix onto the tray for each bhaji, flatten slightly with the back of the spoon.
Bake on the middle shelf of the oven for 20-25 minutes, drizzle a little oil on top of the bhajis and bake for an additional 25 minutes or until golden brown. Serve hot, enjoy!