@jrgm: Oh wow, ok, interesting. I didn't realise.

I just tried to add subdomain.domain.tld into the Route53 console and it certainly accepted it ok. I also just tried it with a niceRoute53.zoneInfo() test (both zoneId and domainName) and they both gave me back the correct thing. Right, let's go with what you already have since it's a whole lot smaller and less of a change! :) Sorry!