Put the onions and celery into a food processor and blend to a fine puree.
Heat the oil in a large saucepan, add the onions and celery and cook on a low heat for 5 minutes.
Add the garlic, cook for 5 more minutes, then add the spices and cook for 1 minute.
Now stir in all remaining ingredients and bring to the boil. Keep on a bubbling simmer uncovered for one hour until the tomatoes are squashy and the liquid has reduced by about a quarter.
Remove the cinnamon stick and blend the sauce until smooth, then sieve into a bowl.
The ketchup will thicken a little when it cools.
CHEF’s TIP
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For a quick cheat you can add Schwartz Sriracha Seasoning to bought ketchup, we’d recommend 1 tsp per 200ml, but go as hot as you dare.
