How can I repair a cut in drywall and make the repair unoticable
Like any other drywall patch - there IS a raised area where the tape is. But you feather compound out 6-12" and there is no NOTICEABLE raised area, as the deviation from "exactly flat" is too small for the eye to see.

Tape with a 4" knife. Re-coat with an 8" knife. Finish with a 12" knife.