Who was Cain's wife?

Question

I saw this problem on reddit today and I think that we cursorily covered this in Tanach class. Who was Cain's wife? In בראשית ד' י"ז it says " וַיֵּדַע קַיִן אֶת-אִשְׁתּוֹ" but it never says who she is. Some of the answers I've seen are that she must be his sister, however it does not mention any other children before this. Furthermore, I don't the "Torah doesn't happen chronologically" card can be pulled here because later, in פסוק כ"ה it says "וַיֵּדַע אָדָם עוֹד, אֶת-אִשְׁתּוֹ". The "עוֹד" means that this must have happened after the birth of קין. The explanation I think was given in class was that his wife was חוה. Is this the case?

Answer 1

The Gemara in Sanhedrin 38b says that Kayin married his twin sister.

The Medrash HaGadol says her name was Kenunoso.

(Source: Tamma DeKra from Rav Chaim Kanievski.)

Answer 2

The Ibn Ezra (5:29) writes:

והשואלים מי היתה אשת קין ושת, מה טעם לשאלה הזאת, כי כתוב באדם ויולד בנים ובנות, וכן כולם`

Those who ask who was the wife of Kain and Sheis, what is the cause for such a question - it is written by Adam that he had sons and daughters...