Learn Dutch: Zodra de zangeres buiten is, roepen de fans haar naam. - As soon as the singer is outside, the fans call her name.

Because the sentence begins with the subordinate clause Zodra de zangeres buiten is. This entire clause takes up the first position of the overall sentence. To satisfy the strict Dutch V2 (verb-second) rule, the finite verb of the main clause (roepen) must take the second position, which places it immediately after the comma and before its subject (de fans).

Is zodra a subordinating conjunction?

Yes. Zodra (as soon as) introduces a subordinate clause. Just like words such as omdat or als, it forces the conjugated verb (in this case, is) to the very end of its clause.

Since we say voordat and nadat, could I say zodra dat?

No, zodra stands perfectly on its own. While voordat (before) and nadat (after) use dat, adding it to zodra is incorrect in standard Dutch. You might occasionally hear native speakers say zodra dat in fast, casual speech, but you should avoid it, especially in writing.

How does the feminine suffix in zangeres compare to other female profession nouns?