8 Roma tomatoes
Apple cider vinegar
Cut Roma tomatoes in half
Arrange tomatoes on an oven rack or tray, and add a drizzle of olive oil, and sprinkle of salt over each.
Roast tomatoes at 135 deg C for 2.5 - 3 hours(!)
Check the tomatoes after this time, they should almost feel like a jam or a jelly.
Put into a blender.
Add a splash of apple cider vinegar and some more salt
Add a little water, and check consistency as you go - it's less about the time, and more about the consistency - you want it to be as smooth as possible.