Recording AVSpeechSynthesizer

I'm trying to record a phrase using AVSpeechSynthesizer.write. It appears to save "something", but when I try to play that back, nothing is played. Not sure where I'm going wrong (wrong file type, not actually saving a file, I don't have the play portion set correctly). Any help would be greatly appreciated. The "speakPhrase" function is just to prove that the AVSpeech is set up properly. That works just fine.

import AVFoundation
import Foundation

class Coordinator {

    let synthesizer: AVSpeechSynthesizer
    var player: AVAudioPlayer?

    init() {
        let synthesizer = AVSpeechSynthesizer()
        self.synthesizer = synthesizer
    }

    var recordingPath:  URL {
        let soundName = "Finally.caf"
        // I've tried numerous file extensions.  .caf was in an answer somewhere else.  I would think it would be
        // .pcm, but that doesn't work either.

        // Local Directory
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return paths[0].appendingPathComponent(soundName)
    }

    func speakPhrase(phrase: String) {
        let utterance = AVSpeechUtterance(string: phrase)
        utterance.voice = AVSpeechSynthesisVoice(language: "en")
        synthesizer.speak(utterance)
    }

    func playFile() {
        print("Trying to play the file")

        do {
            try AVAudioSession.sharedInstance().setCategory(.playback, mode: .default)
            try AVAudioSession.sharedInstance().setActive(true)
            
            player = try AVAudioPlayer(contentsOf: recordingPath, fileTypeHint: AVFileType.caf.rawValue)
            guard let player = player else {return}

                player.play()
        } catch {
            print("Error playing file.")
        }
    }

    func saveAVSpeechUtteranceToFile() {

        let utterance = AVSpeechUtterance(string: "This is speech to record")
        utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
        utterance.rate = 0.50

        synthesizer.write(utterance) { [self] (buffer: AVAudioBuffer) in
            guard let pcmBuffer = buffer as? AVAudioPCMBuffer else {
                fatalError("unknown buffer type: \(buffer)")
            }

            if pcmBuffer.frameLength == 0 {
                // Done
            } else {
                // append buffer to file

                do {
                    let audioFile = try AVAudioFile(forWriting: recordingPath, settings: pcmBuffer.format.settings, commonFormat: .pcmFormatInt16, interleaved: false)
                    try audioFile.write(from: pcmBuffer)
                } catch {
                    print(error.localizedDescription)
                }
            }
        }
    }
}