Pour the oil into a frying pan and set over a medium—high heat. When hot, put in the asafoetida, mustard seeds and cumin seeds in that order. As soon as the mustard seeds begin to pop, a matter of seconds, put in the tomatoes.

Stir once or twice and add the salt, turmeric and cayenne pepper. Stir and add 3 tablespoons Water. Bring to the boil. Cover and cook over a medium—high heat for 5 minutes.

Stir the tomatoes, then add the sugar and ginger. Taste and correct the balance of seasonings if necessary. Cover and cook for another 2—3 minutes.