you can use url rewrite module
add this code to web.config and replace domain.tld with your domain name
<rule name="Remove www" stopProcessing="true">
<match url="^(.*)$" />
<conditions>
<add input="{HTTP_HOST}" pattern="^(www\.)(.*)$" />
</conditions>
<action type="Redirect" url="http://domain.tld{PATH_INFO}" />
</rule>