JSFiddle - React, Tailwind, and code Playground

HTML

<h3><span>{% block hightide_pagename %}{% endblock hightide_pagename %}
    </span></h3>

CSS

h3 {
    display:block;
    position:relative;
    width:100%;
}
h3:after {
    content:"";
    height:1px;
    width:100%;
    background: #000;
    position:absolute;
    top:50%;
}
h3 span {
    background:#fff;
}