Making ketchup from scratch is surprisingly easy, if time consuming (although most of the time is largely hands-off), mostly for the part of making tomato paste. To make the tomato paste, cook about 3 kilos of tomatoes on a low flame until no fluids are present. Then run it through a sieve and mash it with the back of the spoon. Collect the smooth tomato puree, pour it into a pan with 1/2 cup olive oil and cook till the oil separates from the sides of the pan, this will take about 50 minutes.
