Apex domains cannot have CNAME records.
Question and response
Question
dig mittum.com. NS
Answer
mittum.com. 5 NS dns3.elogia.net.
mittum.com. 5 NS dns4.elogia.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0