Apex domains cannot have CNAME records.
Question and response
Question
dig terashima-clinic.com. NS
Answer
terashima-clinic.com. 5 NS ns1.terashima-clinic.com.
terashima-clinic.com. 5 NS ns2.terashima-clinic.com.
Authority
The response has no authority records.
Additional
ns1.terashima-clinic.com. 5 A 213.32.17.67
ns2.terashima-clinic.com. 5 A 51.254.149.19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0