There are things called "megablooms", which happen occasionally, early in the season. Supposed to be several flowers fused together. They produce curiously mishapen tomatoes. Not obvious that's what you have, though.

Yeah, that looks like a megabloom to me, too. Megablooms don't always look like smashed together multiple flowers. A lot of times they look like that one--much larger with more petals and sepals than normal.

Ok, interesting.

Thanks everyone!

should I keep it or cut it?

I'm curious what it will grow into, but will it draw too much energy from the rest of the Inflorescence?

Often, megablooms abort on their own. If it becomes a fruit, it will most likely be a very large but catfaced or deformed fruit (perfectly fine and edible, just misshapen), but sometimes they can end up being relatively normal looking but very large.

It's a personal preference thing. I usually just clip those off because I don't really care about getting super large fruit, and I don't like fruit that's too catfaced. But some people get a kick out of odd fruit and like the possibility of getting a super large fruit.

It won't suck all the life out of your plant. I doubt it would need any more resources from the plant than 2 normal fruits would. It's just a big fused fruit, not a cancer or anything. Sometimes, the truss it's on might need some extra support because of the weight, though.

Lots of discussions here about cut or keep with multiple opinions. So basically it is up to you. Personally I always remove them because the fruit they produce are so deformed they aren't even edible looking and interfere with the normal fruit. But if you are curious to see it....

Dave

It's normal for flowers that look kind of like dandelions to grow on tomato plants on occasion. I don't know if those are megablooms or not, but yours doesn't look like the dandelion-type ones in my garden. It looks more like a giant regular flower (whether or not it actually is a megabloom).

It's very normal to have all flowers take on that appearance on a variety like Riesentomate. If you remove all odd flowers on that variety there I'll be no yield.