We use only the tomato flesh in this recipe. Here is an easy way to remove the skins and seeds: Trim the tomatoes by removing the little stem area and making a superficial criss-cross incision on the underside.

Bring a large pan of water to the boil. On the side, have a large bowl of iced water ready.

Add the tomatoes to the boiling water and cook for a little over a minute, or until you start to see the skin come away. Immediately, use a slotted spoon to remove the tomatoes from the boiling water and plunge into the iced water to prevent further cooking.

Allow to cool completely, then drain well. Slide off and discard the skins of the tomatoes.

Take each tomato, and cut into small wedges (quarter, then quarter again). Use a small paring knife to slide off and discard the seeded area.

You should be left with only the flesh.

Roughly chop up the tomato flesh and place into a mini food processor.

Blitz well until smooth. Add the vinegar, Swerve, salt and white pepper, pinch ground all-spice, pinch celery salt (see the pic about how small these ‘pinches’ should be). Blitz again until the tomato ketchup is the smoothest you can get it. The tomato sauce is ready to use.

As mentioned in the headnote, if you choose to have a more 'cooked' flavour to your ketchup, place the finished product for 10-15 minutes in a pan over moderate heat until it thickens and slightly darkens. Allow to cool and then store in the fridge for no longer than 4 days.