Apex domains cannot have CNAME records.
Question and response
Question
dig yi.org. NS
Answer
yi.org. 5 NS fumo-viridus.crackerjack.net.
yi.org. 5 NS connubialis.crackerjack.net.
Authority
The response has no authority records.
Additional
connubialis.crackerjack.net. 5 A 45.79.222.218
fumo-viridus.crackerjack.net. 5 A 139.162.218.233
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0