Siewert, a surname of German origin, is pronounced as /ˈziːvərt/. In IPA phonetic transcription, the "s" is represented by the /s/ sound, followed by the long "e" sound represented by the /i:/ letter combination. The "w" is pronounced as an /v/ sound, while the "er" is represented by the /ər/ sound, giving the final syllable the sound /vərt/. Therefore, the correct spelling of this surname is S-i-e-w-e-r-t, with the "e" and "w" separated by an "i".