Apex domains cannot have CNAME records.
Question and response
Question
dig cc. NS
Answer
CC. 4 NS ac2.nstld.com.
CC. 4 NS ac3.nstld.com.
CC. 4 NS ac4.nstld.com.
CC. 4 NS ac1.nstld.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0