Apex domains cannot have CNAME records.
Question and response
Question
dig altospam.com. NS
Answer
altospam.com. 5 NS ns1.oktey.eu.
altospam.com. 5 NS ns1.oktey.com.
altospam.com. 5 NS ns2.oktey.eu.
altospam.com. 5 NS ns2.oktey.com.
altospam.com. 5 NS ns3.oktey.eu.
altospam.com. 5 NS ns4.oktey.eu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0