Ce que (vs ce qui) = what, which (relative pronouns)

Question

Why can't you say Dis-moi quetu fais le weekend.Dis-moi ce que tu fais le weekend.

Accepted Answer

The 2nd sentence is grammatically correct. The question relates to the whole idea of 'WHAT you do on the weekend' and this requires 'ce que' (followed by the subject pronoun in this case). Que cannot be used (none of its translations fit to give a meaningful sentence).
These related lessons should help clarify -
https://french.kwiziq.com/revision/grammar/when-to-use-que-to-say-whom-which-or-that-relative-pronouns
 
https://french.kwiziq.com/revision/grammar/ce-que-what-which-relative-pronouns