A better way to phrase "his masterwork" or "his epic"?

In the context of an artist. Like, let's say, Dali's "melting clocks" painting; we would call that his (blank), AKA his most recognizable/meaningful/popular/"epic" work.

I think there is, perhaps, a French/Latin term Americans use? I'm not sure...

Solution 1:

To my mind, magnum opus stands far above the rest as the term one would use in this context.

Solution 2:

Dalí’s Persistence of Memory is considered to be his signature work; it’s the painting that people most commonly associate with him.

Here, signature is used in this sense:

a distinctive pattern, product, or characteristic by which someone or something can be identified