The spelling of the word "pieroni" can be explained using the International Phonetic Alphabet (IPA). The initial sound is /p/, followed by the long /i/ sound as in "pea". Then comes the /r/ sound, followed by another long /o/ sound, as in "go". Finally, we have the nasal sound /n/ and the short sound /i/ as in "pin". So, in IPA transcription, "pieroni" is spelled /pɪərəʊni/.