Let’s be generous in our definition of “transgressive” - if a food could shock you and/or people whose opinions you care about, for cultural, religious, health, aesthetic, or other reasons, it counts.
I ate endangered sea turtle in Micronesia in 1988. The turtle was a gift, given with great respect, from some outer islanders to the president of the Federated States of Micronesia. The roasting and consumption was done with considerable fanfare. It was one of those situations where there was no morally unambiguous answer, it was simply a question of which principle one decided to violate.
I ate the turtle. It was delicious.