Tomato ketchup (or catsup) is an essential food group for many people - they put it on everything. I think that's a bit excessive, but I do like it with chips or french fries, and sometime on a burger. If you make your own, you can get a more robust flavour and texture than the commercially produced stuff.
Peel and roughly chop the onion, quarter the tomatoes, crush the garlic and break up the cinnamon stick. Add all the ingredients except the salt to a large pan and bring to the boil. When boiling, reduce the heat to a simmer and put a lid on it. Give it a stir every ten minutes or so to make sure it's not sticking.
After an hour, turn off the heat, pop the pan contents into a blender and whizz until smooth. Now pass it through a fine seive, using the back of a large spoon to force the ketchup through the mesh. You'll be left with a small amount of pulp which should be discarded.
Put the ketchup into a small pan, and heat gently until it acheives the correct ketchuppy consistency. Add the salt and taste the ketchup. You're looking for a balance between the salt, sugar and vinegar, so add extra of either if you cannot taste it.
When the ketchup is completely cool, spoon it into a sterile screw-top jar. It should keep for a few months unopened. Once opened, keep it in the fridge.