Apex domains cannot have CNAME records.
Question and response
Question
dig volcdns.com. NS
Answer
volcdns.com. 1 NS ns2.volcengine-dns.com.
volcdns.com. 1 NS ns1.volcengine-dns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0