Apex domains cannot have CNAME records.
Question and response
Question
dig tanomail.com. NS
Answer
tanomail.com. 5 NS ns4.otsuka-shokai.co.jp.
tanomail.com. 5 NS ns2.otsuka-shokai.co.jp.
tanomail.com. 5 NS ns21.tayoreru.com.
tanomail.com. 5 NS ns6.otsuka-shokai.co.jp.
Authority
The response has no authority records.
Additional
ns2.otsuka-shokai.co.jp. 1 A 157.205.233.249
ns4.otsuka-shokai.co.jp. 1 A 111.87.26.249
ns6.otsuka-shokai.co.jp. 1 A 157.205.232.118
ns2.otsuka-shokai.co.jp. 1 AAAA 2403:6c00:300b:e910:0:0:28:249
ns4.otsuka-shokai.co.jp. 1 AAAA 2001:268:806:100:0:0:36:249
ns6.otsuka-shokai.co.jp. 1 AAAA 2403:6c00:300a:e810:0:0:196:249
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0