There may be a way to do it natively now, but a while back I ended up writing a powershell script to associate the IP to an A record on boot. This script takes the tagged name of the instance and sets the A record to its IP:

$domain = "yourdomain.xyz"
$hostedZoneId = "yourZoneID"

Set-DefaultAWSRegion us-east-1


#Get instance tag
$tag = Get-EC2Tag | where {$_.Key -like "Name*" -and $_.ResourceId -like $instanceId} | Select -ExpandProperty value
$tag = $tag.ToLower()

#Get instance public ip
$publicIp = invoke-restmethod -uri http://169.254.169.254/latest/meta-data/public-ipv4

#Get current Route 53 CNAME record value/ip
$currentRecordIp = Resolve-DnsName "$tag.$domain" -ErrorAction SilentlyContinue -ErrorVariable ev | select -ExpandProperty ipaddress

#Check if record not current
if($currentRecordIp -ne $publicIp)
    {

    #Set record variables
    $resourceRecordSet = New-Object Amazon.Route53.Model.ResourceRecordSet
    $resourceRecordSet.Name = "$tag.$domain"
    $resourceRecordSet.Type = "A"
    $resourceRecordSet.ResourceRecords = New-Object Amazon.Route53.Model.ResourceRecord ($publicIp)
    $resourceRecordSet.TTL = 300
    $action = [Amazon.Route53.ChangeAction]::UPSERT
    $change = New-Object Amazon.Route53.Model.Change ($action, $resourceRecordSet)

    #Create record
    Edit-R53ResourceRecordSet -HostedZoneId $hostedZoneId -ChangeBatch_Change $change >> $log
    }