Serious Eats: Talk
First note - I came up with this recipe for my kids so it is as close to supermarket ketchup as you can get and still be homemade. They eat ketchup on a lot of stuff because it is a great way to get them to eat things they might otherwise shun. The hubs and I eat it occasionally on burgers but not much of anything else so this is a kid friendly recipe. As I mentioned in the other thread, nobody I've ever served it to has realized until I told them that it isn't Heinz. The reason I make it myself is so that I know what goes into it.
Second note, I have on more than one occasion made my own tomato paste but in this version I use commercially canned organic tomato paste. Again, this was developed for my kids and the homemade tomato paste turns a darker color that adults don't mind at all but kids find suspicious.
Also, the recipe doubles, triples, quadruples easily. If I get to Costco and can buy large quantities of agave, I make a big old vat of this and store it in my basement fridge or boiling water bath can it for 20 minutes for shelf storage.