Apex domains cannot have CNAME records.
Question and response
Question
dig seishiro.net. NS
Answer
seishiro.net. 4 NS ns-989.awsdns-59.net.
seishiro.net. 4 NS ns-699.awsdns-23.net.
seishiro.net. 4 NS ns-370.awsdns-46.com.
seishiro.net. 4 NS ns-1465.awsdns-55.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0