Apex domains cannot have CNAME records.
Question and response
Question
dig mazda.com. NS
Answer
mazda.com. 5 NS rx7.mazda.co.jp.
mazda.com. 5 NS ns2.mazda.co.jp.
Authority
The response has no authority records.
Additional
rx7.mazda.co.jp. 5 A 210.154.137.152
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0