Store-bought ketchup is full of sugar and preservatives, whereas the homemade kind takes twenty minutes of active work and you can tune the flavour yourself: smokier, tangier or less sweet. It's great with burgers, fries and hot dogs.
Canned peeled tomatoes work instead of passata, but blend them smooth first with a stick blender, otherwise the ketchup stays chunky.
For a smokier flavour, add half a teaspoon of smoked paprika or a few drops of liquid smoke.
Don't cook it covered: the steam can't escape and the ketchup stays thinner.
Poured hot into a jar and sealed well, it keeps in the fridge for about 2 weeks; small portions can be frozen in an ice cube tray.
Frequently asked questions
How long does homemade ketchup keep?
About 2 weeks in the fridge in a clean jar, and 2-3 months in the freezer. It has no preservatives, so it spoils sooner than store-bought ketchup.
Why does ketchup need vinegar?
Vinegar provides the characteristic tang and also preserves a little; without it the tomato would taste flat and too sour, which is why both vinegar and sugar are needed.