What is cibrèo? Well, it isn't the kind of dish that you'd guess a dour-looking woman like Catherine would have enjoyed. But apparently she adored it. Now, let me provide a more direct answer to that question.
Cibrèo was a dish that originated in Catherine's native Florence. It is (and was) usually made with the gizzard, liver, testicles, and cockscomb of a young rooster, which is mixed with beans and egg yolks and then served on toast.
So it sounds like cibrèo is to Florence what haggis is to Scotland.