Apex domains cannot have CNAME records.
Question and response
Question
dig mx2.nifty.com. NS
Answer
mx2.nifty.com. 5 NS ns-186.awsdns-23.com.
mx2.nifty.com. 5 NS ns-1276.awsdns-31.org.
mx2.nifty.com. 5 NS ns-573.awsdns-07.net.
mx2.nifty.com. 5 NS ns-1990.awsdns-56.co.uk.
Authority
The response has no authority records.
Additional
ns-1276.awsdns-31.org. 2 A 205.251.196.252
ns-1276.awsdns-31.org. 2 AAAA 2600:9000:5304:fc00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0