JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content1"><div class="contentInner">Text1</div></div>
<div class="content1"><div class="contentInner">Text2</div></div>
<div class="content1"><div class="contentInner">Text3</div></div>

CSS

.content1:first-child{text-decoration:underline;}