Apex domains cannot have CNAME records.
Question and response
Question
dig 144.34.172.141.16clouds.com. NS
Answer
144.34.172.141.16clouds.com. 5 NS ns1.16clouds.com.
144.34.172.141.16clouds.com. 5 NS ns2.16clouds.com.
Authority
The response has no authority records.
Additional
ns1.16clouds.com. 5 A 212.83.179.179
ns2.16clouds.com. 5 A 54.39.173.11
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0