Apex domains cannot have CNAME records.
Question and response
Question
dig enginemailer.org. NS
Answer
enginemailer.org. 5 NS dns102.a.register.com.
enginemailer.org. 5 NS dns011.c.register.com.
enginemailer.org. 5 NS dns195.b.register.com.
enginemailer.org. 5 NS dns177.d.register.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0