RRSet of type CNAME with DNS name is not permitted at apex in zone
This error happens on trying to configure CNAME record for the domain to point to loadbalancer DNS name.
This is the default behavior and see the reference below.
As per RFC1912 section 2.4:
A CNAME record is not allowed to coexist with any other data. In other words, if suzy.podunk.xx is an alias for sue.podunk.xx, you can't also have an MX record for suzy.podunk.edu, or an A record, or even a TXT record. Especially do not try to combine CNAMEs and NS records like this!: podunk.xx. IN NS ns1 IN NS ns2 IN CNAME mary mary IN A
Route53 provides another option "alias records" in-order to resolve this problem. We can configure loadbalancer DNS name as A record alias without any issues.