That looks like a big bite
and if the dark spot is a hole, you might find the culprit inside. But it is definitely one of the bigger pests, a caterpillar or a slug!
I had slugs in the greenhouse one summer and they wreaked havoc on my tomatoes as soon as they blushed.
For caterpillar your BT for caterpillars is the remedy of choice.
It doesn't affect beneficials but specifically the caters. For slugs there's a pelleted product that goes under several names, Slug B Gone is one if I recall, which is an iron compound, again, harmless to other things but deadly to the slug, you sprinkle it on the ground. I have seen it work really well on brassicas and greens at the farm, but for some reason did not attract the slugs that were hiding in my containers and climbing up to eat succulent tomato at night.
They knew what they wanted.
I don't know if DE works on slugs? Maybe if you sprayed it on the lower stem really heavily that would stop them from climbing up. Otherwise it is pretty broad spectrum so could affect good bugs as well as bad, if you spray it everywhere.
Spinosad is for leaf miners, thrips, spider mites and other tiny things. This is not what bit your tomato fruit for sure, but if you see a lot of tiny leaf damages again (I never see the critters themselves) then maybe worth a go. I know I have mites in my greenhouse that are always followed by hordes of tiny spiders, so small I can only assume they eat the littler guys. Both mites and spiders then disappear a few weeks later. I considered DE for mite control but will wait and see how the spiders do first. If the mites keep coming I'll DE the leaves. If I had Spinosad I would consider that too.