If you want an unsuccessful batch of canned tomatoes, do what I did and follow all the directions to the letter and then don't put enough water in the canner because you think it is going to bubble over. This will ensure your jars don't seal properly and you will have spent all day canning for naught. Nice job.
I started out doing it all just as Ferdzy over at Seasonal Ontario Food said. I even got the bottled lemon juice (which I didn't want to do because of the plastic, but you HAVE to do as it's the only way to ensure you have an even acidity level). I peeled and chopped the tomatoes, sterilized jars, and boiled the tomato filled 1L jars for 45 min for each batch (I had 2 batches). But when I put them in the water I was reluctant to have the water right up to the rim of the canner so I probably ended up with only 3/4 of an inch of water over the jars instead of 1 inch. And by the end of the 45 mins there was probably only .2 of an inch over the jars.
And dang it if 4 of the 11 jars didn't seal (I put those 4L promptly in the freezer). AND on top of that, of the remaining sealed jars, most are questionable (I think). Here's what I'm worried about - see the one on the left? How its floating and the tomatoes are all sucked up to the top? That's what I think it should look like (all my salsa jars look like that). To me that really means they are sealed up properly. See the one on the right? It's floating but the tomatoes aren't all sucked up to the top. And see the one in the middle? It isn't floating at all.
Now technically all of them are sealed like I said. I even tested them by taking off the rings and lifting them by the flat lid part. And the lid stayed on.
So are they all ok to eat?
I might cry if the only one that is safe to eat is the on on the left because there is only one jar like that. Ok, I won't cry. But I will have learned a valuable lesson. The hard way.
If you are thinking of canning tomatoes, I'd recommend following Ferdzy's instructions and also check out the USDA's canning instructions. And definitely, DEFINITELY, fill that canner right to the top!