Apex domains cannot have CNAME records.
Question and response
Question
dig nasdns.net. NS
Answer
nasdns.net. 5 NS ns10.nasdns.net.
nasdns.net. 5 NS ns5.nasdns.net.
Authority
The response has no authority records.
Additional
ns5.nasdns.net. 5 A 38.98.87.19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0