add olive oil to a pan and add your roughly chopped onion. Sweat down for 10-15 mins on low with no colour...
make your spice packet by placing all of your herbs and spices into your cheese cloth and securing with the kitchen twine...
Add tomatoes, salt, vinegar, sugar and your spice packet to your onions and cook for around 30 mins on medium until mushy...
Now remove your spice packet and discard...
You can at this point blend your ketchup to strain in but I just pushed it through a fine sieve without blending...less washing up...
Now put back on the heat and cook down to your desired consistency. Some where around 45 mins worked for me...
Enjoy!