Use of Ser in "what is your favorite food?"

I see the link for below, and I don't see why it is cual es* tu comida favorita**.** Which criteria is it meeting in the Ser category?

Is it "characteristic"? Because I consider that more of a characteristic of me, rather than of the object. Is it a matter relation? I assume not – because I thought this relation was usually referring to relationships between people. I just don't get it, because I was pretty sure that Estar would be correct here, because to me it seems like a condition. (This week, chocolate flavor is my favorite, but perhaps next week a new flavor will come out that will become my favorite, and chocolate will lose its special status, lol).,and%20actions%20(temporary%20states)).

submitted by /u/membranedweller
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