Great question — answering as the UphillTech team:
The USA has restrictions on the import of food items. Some information is given here . I have on one occasion forgotten items I bought before boarding, intending to snack on the flight. These were detected by a sniffer dog in the immigration queue and the items confiscated - I was not otherwise penalised, but I could have been fined. In your case I guess that the tomato would have been the issue.
Full answer by djna: https://travel.stackexchange.com/a/104315 (CC BY-SA 3.0).
Want it for your business? UphillTech.