The best primary source is Appendix E of the Lord of the Rings, which covers pronunciation of both vowels, consonants and stress:

In words of two syllables it falls in practically all cases on the first syllable. In longer words it falls on the last syllable but one, where that contains a long vowel, a diphthong, or a vowel followed by two (or more) consonants. Where the last syllable but one contains (as often) a short vowel followed by only one (or no) consonant, the stress falls on the syllable before it, the third from the end. Words of the last form are favoured in the Eldarin languages, especially Quenya.

So it would probably be Beren and Luthien if you view the name as a three-syllable name (loo-THEE-en), or Luthien if you read it as LOO-theen.

The best primary source is Appendix E of the Lord of the Rings, which covers pronunciation of both vowels, consonants and stress:

In words of two syllables it falls in practically all cases on the first syllable. In longer words it falls on the last syllable but one, where that contains a long vowel, a diphthong, or a vowel followed by two (or more) consonants. Where the last syllable but one contains (as often) a short vowel followed by only one (or no) consonant, the stress falls on the syllable before it, the third from the end. Words of the last form are favoured in the Eldarin languages, especially Quenya.

So it would probably be Beren and Luthien if you view the name as a three-syllable name with a long middle sound (loo-THEE-en), or Luthien if you read it as LOO-theen or (as Tolkien probably intended it) LOO-thi-en.

The best primary source is Appendix E of the Lord of the Rings, which covers pronunciation of both vowels, consonants and stress:

In words of two syllables it falls in practically all cases on the first syllable. In longer words it falls on the last syllable but one, where that contains a long vowel, a diphthong, or a vowel followed by two (or more) consonants. Where the last syllable but one contains (as often) a short vowel followed by only one (or no) consonant, the stress falls on the syllable before it, the third from the end. Words of the last form are favoured in the Eldarin languages, especially Quenya.

So it would probably be Beren and Luthien.

The best primary source is Appendix E of the Lord of the Rings, which covers pronunciation of both vowels, consonants and stress:

In words of two syllables it falls in practically all cases on the first syllable. In longer words it falls on the last syllable but one, where that contains a long vowel, a diphthong, or a vowel followed by two (or more) consonants. Where the last syllable but one contains (as often) a short vowel followed by only one (or no) consonant, the stress falls on the syllable before it, the third from the end. Words of the last form are favoured in the Eldarin languages, especially Quenya.

So it would probably be Beren and Luthien if you view the name as a three-syllable name (loo-THEE-en), or Luthien if you read it as LOO-theen.