Apex domains cannot have CNAME records.
Question and response
Question
dig rocketseed.com. NS
Answer
rocketseed.com. 4 NS pdns05.domaincontrol.com.
rocketseed.com. 4 NS pdns06.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0