"Who works on Sunday?"
Translation:¿Quién trabaja el domingo?
Yes & no, "El domingo" would literally translate to "the Sunday", but the literal translation sounds funny. To answer, why "el domingo", there are two take-aways.
1) Spanish does not have a direct translation for "on" when referring to dates. http://www.spanishdict.com/translate/on
2) There are many times when Spanish will use an article to specify a noun and English will not.
I hope this helps. :)
Yo would be trabajo, but you were right with the idea that there is no pronoun
This website is fun (divertido) to use but the comment section is a huge help. The little explanations at times make a great deal of sense and seeing it helps me to remember it.