Roughly cut the tomatoes into chunks, then thinly slice the onions. Finely chop the chilli and grate the ginger.
Put everything in a heavy-based pan, then bring to the boil. Turn down the heat and gently simmer for about 60 minutes until you get a thick, sticky jam. There shouldn’t be much liquid left around the veggies, but it shouldn’t be solid either.
Let it cool in the pan, then spoon it into 2 sterilized jars.
Store in a cool place.
Serve it with cheese, cold meat or as garnish on party nibbles.