The spelling of "Cavness" can be somewhat tricky as the pronunciation differs slightly from the way it is spelled. The IPA phonetic transcription of this word is /ˈkævnəs/. As you can see, the "a" in the first syllable is pronounced as "æ" similar to the "a" in "cat" and the "e" in the second syllable is almost silent. Therefore, the correct way to spell "Cavness" is without a second "e" - Cavness.