edit: Amazon now supports this. http://aws.typepad.com/aws/2012/12/root-domain-website-hosting-for-amazon-s3.html
I have my domain config in Route53 at Amazon AWS
exec ping command in my domain without www
$ ping gabster.com.br ping: cannot resolve gabster.com.br: Unknown host
exec ping command in my domain with www
$ ping www.gabster.com.br PING s3-website-sa-east-1.amazonaws.com (188.8.131.52): 56 data bytes 64 bytes from 184.108.40.206: icmp_seq=0 ttl=244 time=25.027 ms 64 bytes from 220.127.116.11: icmp_seq=1 ttl=244 time=25.238 ms 64 bytes from 18.104.22.168: icmp_seq=2 ttl=244 time=25.024 ms
Route 53 -> Create Record Set -> Name: [ ].gabster.com.br Set CNAME value: www.gabster.com.br
"RRSet of type CNAME with DNS name mydomin.com is not permitted at apex in zone mydomin.com"