Apex domains cannot have CNAME records.
Question and response
Question
dig xn--9dbq2a. NS
Answer
xn--9dbq2a. 5 NS ac1.nstld.com.
xn--9dbq2a. 5 NS ac2.nstld.com.
xn--9dbq2a. 5 NS ac3.nstld.com.
xn--9dbq2a. 5 NS ac4.nstld.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0