Apex domains cannot have CNAME records.
Question and response
Question
dig coolhousing.net. NS
Answer
coolhousing.net. 3 NS ns1.websupport.cz.
coolhousing.net. 3 NS ns3.websupport.eu.
coolhousing.net. 3 NS ns2.websupport.cz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0