Mix all together and chill before serving to allow flavours time to marry.
You could freeze the juice off the tinned tomatoes for use in a pasta or other sauce.
Notes
The tin of tomatoes should be about 28 oz (800 ml).The 4 separate fresh tomatoes help to give it a nicer texture. Red onion is nice, but don't sweat it.If you can't get fresh coriander or have people who don't like it, try parsley. It won't taste the same, but just don't use dried coriander.You can store this salsa covered in the refrigerator for up to 3 days. Use by then.