Except for the position of the damage, high on the plant, this looks like snail damage. No other damage elsewhere.
Rats will do that abut I don't see the telltale toothmarks. Another chomper is the tomato/tobacco hornbeam (a caterpillar).
I just found and killed 4 huge hornworms.
The damage done does look like what I have seen done by the Tomato Hornworm. These are the larva of either the Carolina Sphinx or the Five Spotted Hawkmoth, both members of the Sphinx Moth family. There may be someone that tells you that these are the larva of the Hummingbird Moth but they are not, same family but only cousins not siblings.
You can control these buggers by hand control, if you do not have many plants. A good, early development stage, control is Bacillus thuringiensis - Kurstaki, BTK sold as a number of different products, but the larva needs to be fairly young for it to work. Apparently Neem Oil products can also work. There are some other products but most are so toxic that no one should be using them, especially on plants that grow food they eat.
If the larva have what looks like grains of rice sticking out of them then you have a wasp that has laid eggs in that larva and they are eating it alive. Do no harm to that Tomato Hornworm and the wasps larva will grow and become more wasps to help you control these wee buggers.
Oops. Meant to say tomato/tobacco hornworm (sigh) Glad you figured it out!
In the light of day, I found more damaged tomatoes for a total of 5 so far. I also found some leaf damage, then turned the leaf over to find a small hornworm, which got crushed. Now I need to inspect the plants every day and night.
Hey! A crushed hornworm is a wasted hornworm!
Here is a link that might be useful: Click to see!
I'd much rather waste a hornworm than waste a tomato.
Oh well, you missed my point or I didn't make it very well. Rather than stomp on the caterpillar after you find them, toss them into a bird bath, or into the lawn where the birds will find them.
But that's me....I get it that not everyone is going to bother to do that.
You can feed these wee buggers to your birds, although as much as they like them why the birds do not seem able to find them on the tomato plants escapes me, but you will need to be sure you put them someplace they cannot escape from. I have seen these buggers making a beeline back to the tomatoes, they do move fast.
When I get through with them. They don't move at all. I've had too much bird damage to want to feed them.
That seems like too clean and even of a cut on the tomato, like from a knife or one big chomp of a large animal. From my experience and pictures, hornworms don't seem to leave such even damage. It's more bumpy and pitted.
So some of you have already seen hornworms this year? Where are you at? I check my plants daily, and wonder when they'll show up in south Texas. I wish there was a Sphinx Moth / Hornworm monitoring alert page, where people could get updates as to where they've been seen. Could trend where they are heading, etc.
I found 2 more hornworms, but very little more damage. If it was earlier in the season, I would use BT.