Apex domains cannot have CNAME records.
Question and response
Question
dig heliohost.org. NS
Answer
heliohost.org. 5 NS ns1.heliohost.org.
heliohost.org. 5 NS ns2.heliohost.org.
Authority
The response has no authority records.
Additional
ns1.heliohost.org. 5 A 65.19.143.3
ns2.heliohost.org. 5 A 64.62.211.133
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0