JSFiddle - React, Tailwind, and code Playground

HTML

<h2>Gucki hier, dein kleiner Text</h2>
<p>
Lorem ipsum dolor sit irgendwas.
</p>



<h2 class="center">Gucki hier, dein kleiner Text</h2>
<p>
Lorem ipsum dolor sit irgendwas.
</p>

CSS

h2:before {
  content: "";
  display: block; width: 5em; height: 0.2em;
  border-top: 5px solid red;
}

h2 {
    background-color: #ccf;
}
h2.center {
    margin: auto; width: max-content;
}
h2.center:before {
  margin:auto;
}