Apex domains cannot have CNAME records.
Question and response
Question
dig uem.mz. NS
Answer
uem.mz. 2 NS oceano.uem.mz.
uem.mz. 2 NS anyns.uem.mz.
uem.mz. 2 NS dzowo.uem.mz.
uem.mz. 2 NS ns-mz.afrinic.net.
uem.mz. 2 NS zebra.uem.mz.
uem.mz. 2 NS phloem.uoregon.edu.
Authority
The response has no authority records.
Additional
anyns.uem.mz. 152996 A 204.61.216.14
dzowo.uem.mz. 153029 A 196.3.96.66
zebra.uem.mz. 113800 A 196.3.96.67
oceano.uem.mz. 153029 A 196.3.96.69
phloem.uoregon.edu. 2 A 128.223.32.35
phloem.uoregon.edu. 2 AAAA 2001:468:d01:20:0:0:80df:2023
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0