Chullin 112 - "Taste, the Son of a Taste"

If fish was roasted on the fire and taken directly from the fire - while still hot - and placed on a clean meat plate, then the fish absorbs the taste of meat, which in turn has been previously absorbed by the plate. The fish is thus removed from direct contact with meat, and its taste of meat is what is called "taste, the son of a taste." Rav said about this imparted meat taste that this fish should not be eaten with milk products, but Shmuel said that it is permitted.

Rav Elazar was once serving Shmuel at a meal, and they brought Shmuel such fish, and he ate it with a sauce made with milk. He offered some to Rav Elazar, who refused. Shmuel then said, "I served it to your teacher, Rav, and he ate!" When Rav Elazar asked Rav about this, Rav said, "Shmuel could not serve me anything forbidden!" Indeed, the law follows Shmuel.

By extension, even fish cooked in a meat pot or roasted on a meat spit can be served with dairy foods, although one should not knowingly create such a situation.

Art: Frederic Bazille - Still Life with Fish