The correct spelling of the word pronounced as "up pie" is "apple pie". In IPA phonetic transcription, it would be written as /ˈæpəl paɪ/. The first syllable is represented by the vowel sound "æ", which is pronounced similar to the a in "cat". The second syllable begins with the consonant cluster "p-" followed by a short "a" sound and ends with a long "i" sound. The proper spelling of words allows for clear communication and understanding in both spoken and written language.