Slice the red onion, ginger, garlic and tomatoes and set aside. Note that as we are blending everything into a paste, the pieces do not have to be perfectly sized!
Add 1 tsp of the sunflower oil to a medium-sized saucepan over medium-low heat. Add the chopped red onion and saute for 3-5 minutes until it is soft and slightly golden.
Add the chopped ginger and garlic to the pan. Saute for just a minute until they are fragrant.
Add the chopped tomatoes and salt to the pan. Cook for one minute to soften the tomatoes slightly.
Add the ground turmeric, ground coriander, ground cumin, garam masala and chilli powder. Stir and continue cooking for 3-5 minutes until the aroma changes. The spices will no longer smell raw and the smell of the curry paste will be noticeably more fragrant.
Set aside the curry paste to cool for a few minutes whilst you drain and rinse a can of chickpeas.
Add the curry paste to a blender jug along with about 2 tbsp of the chickpeas (this will help to thicken the curry paste). Blend until creamy and smooth, adding 1-2 tbsp of water if needed to help it blend.
Make the tadka/vagar in a fresh medium-sized saucepan: Add the remaining 1 tsp of oil along with the cumin seeds, cloves, cardamom pods, and cinnamon stick.
Place the saucepan over medium-high heat and wait for the spices to crackle as the oil heats up. At this point, lower the heat and add the blended curry paste, canned chickpeas, green chilli, and approximately 1 cup of cold water.
Stir everything together and bring it to the boil. Simmer on medium-low heat for 10-15 minutes until the chickpeas have softened and the gravy is thick.
Taste the chana masala for salt and add more water at this point if you prefer a thinner gravy.
Just before serving, stir in the kasuri methi. For a richer taste, stir in 1-2 tbsp of single cream (optional). Garnish with coriander leaves and serve with hot, fluffy naan. Enjoy!