Apex domains cannot have CNAME records.
Question and response
Question
dig 80216bdbea2363da2a2d11665d2352630509c68bcb4e67331d8c7293.eu.rspf.letsdmarc.com. NS
Answer
80216bdbea2363da2a2d11665d2352630509c68bcb4e67331d8c7293.eu.rspf.letsdmarc.com. 5 NS ns3.letsdmarc.com.
80216bdbea2363da2a2d11665d2352630509c68bcb4e67331d8c7293.eu.rspf.letsdmarc.com. 5 NS ns4.letsdmarc.com.
80216bdbea2363da2a2d11665d2352630509c68bcb4e67331d8c7293.eu.rspf.letsdmarc.com. 5 NS ns1.letsdmarc.com.
80216bdbea2363da2a2d11665d2352630509c68bcb4e67331d8c7293.eu.rspf.letsdmarc.com. 5 NS ns2.letsdmarc.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0