Put the finely chopped onion and garlic in a pot with 2 cm of water and soften under a medium high heat for 5-7 minutes, adding more water if necessary.
Add the cumin seeds and stir for a further two minutes. Add the chilli powder, coriander, fresh ginger and garam masala and keep stirring for another two minutes.
Add the tin of tomatoes and the tin of chickpeas. Stir all the ingredients together and heat through for about 10 minutes.
Add the tamarind paste and taste. Adding a little salt if desired.
Add the spinach and stir. As soon as the spinach has wilted, serve with brown rice.