Heat vegetable oil in a large pan, add the onion and cumin seeds and cook for approximately 3 – 4 minutes stirring until the onions are softened.
Add the salt, red chilli powder, turmeric powder and ginger and garlic paste and cook, stirring everything together for about a minute.
Then add the chopped tomato and cook for a couple of minutes then stir in the tomato puree and water and allow the tomato mixture to simmer and soften.
Blitz the tomato mixture to a paste in a blender or food processor and return to the pan.
Heat the pan until the paste is simmering and add the diced potato and cook, stirring occasionally until the potato is softened.
Put the chopped spinach into the pan and combine it with the potato mixture until softened then stir in the fenugreek.