You did nothing 'wrong' but put tomatoes in the compost bin and the seeds were not killed. It is very difficult to make weed-free compost. You just have to accept this and keep pulling the weed seedlings out as they grow and they should pull easily.

we did this one year with little green toms and this happened . I even potted a couple on and the resulting toms were really nice.

Remember that home created compost does not normally get hot enough to kill weed or other plant seeds. You can compost the tomato stems but not the fruit - big or small...

Agree - there is a way to create a hot, aerobic compost heap, but the heap must be a minimum of a metre cubed, and it must be turned 2 - 3 times a week, monitored for moisture levels, not too wet, not too dry. If you're not going to do that (and most of us don't) then what you've got is a cold, anaerobic compost heap. Nothing wrong with that, but nothing with seeds should be added to it because, as you've discovered, they will survive the composting process.

Thank you for all my replies very helpful .