Apex domains cannot have CNAME records.
Question and response
Question
dig dnshigh.com. NS
Answer
dnshigh.com. 5 NS ns2.dnshigh.com.
dnshigh.com. 5 NS ns1.dnshigh.com.
Authority
The response has no authority records.
Additional
ns1.dnshigh.com. 5 A 185.81.7.130
ns2.dnshigh.com. 5 A 46.16.90.21
ns2.dnshigh.com. 5 A 46.30.244.60
ns2.dnshigh.com. 5 A 51.91.199.128
ns2.dnshigh.com. 5 AAAA 2001:41d0:266:bf00:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0