What can you do with a glut of tomatoes? Make your ketchup in a slow-cooker! It simmers at just the right temperature, it doesn't burn, you don't have to stir it, and you don't get a kitchen full of vinegar fumes.

You can even put the slow-cooker outside if you like (though in England this year, it's usually raining...)

Step 1: Ingredients

About 1 kg tomatoes
1 small onion
2 sticks celery
4 - 5 tablespoons brown sugar
2 tablespoons tomato puree
1 tablespoon paprika
1 tablespoon mustard
Up to 2 teaspoons chilli powder
2 teaspoons salt
0.5 teaspoon ground allspice
1 teaspoon tamarind paste
100 ml white wine vinegar

Step 2: Cook the Sauce

Finely chop the onion and celery. Roughly chop the tomatoes. Mix everything in the slow- cooker. Cook on high for 30 minutes, then stir and cook for 8 - 10 hours on low. Cool.

Step 3: Purée the Sauce

Use a hand blender to puree the sauce. Pass through a sieve to remove the seeds and skins. Re-cook on high for 2 hours to make sure the sauce is sterile before bottling.

Step 4: Bottle the Sauce

Wash the bottles in hot soapy water, then dry in a low oven.

Use a ladle and funnel to transfer the sauce to the bottles. Cover immediately. Label when cold.

If you want to store the sauce for a long time, it should be sterilised - I have explained a way to do this in another instructable!

https://www.instructables.com/id/Sterilise-Preserves-With-A-Sous-vide-Water-Bath/