Why is $DEFAULT_SITE_URL appearing in entries URL?

I have an entry loop on my homepage that uses {{ entry.url }} that links to the full entry. When I click on the entry, the url looks like this

mydomain.com/$DEFAULT_SITE_URL/the-entrys-slug

Even though my section settings just has the Entry URI Format set to {slug}

Here’s my entry loop if you need it

{% set aBetterPost = craft.entries.section('aBetterPost').limit('6').all() %}
{% for entry in aBetterPost %}
    <div class="main-post">
        <a href="{{ entry.url }}">
            Entry Stuff...
        </a>
    </div>
{% endfor %}

How can I get rid of the $DEFAULT_SITE_URL ?