Apex domains cannot have CNAME records.
Question and response
Question
dig mdl.net. NS
Answer
mdl.net. 5 NS sfe01.mdl.net.
mdl.net. 5 NS sfe02.mdl.net.
Authority
The response has no authority records.
Additional
sfe01.mdl.net. 5 A 195.22.225.11
sfe02.mdl.net. 5 A 195.22.225.34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0