JSFiddle - React, Tailwind, and code Playground

HTML

<h1>
  My Title
</h1>

CSS

h1{
    font-size: 32px;
    position:relative; 
    padding:10px 5px; 
    border-bottom:1px solid #000; 
    display: inline-block;
}

h1:before {
    content:""; 
    display:block; 
    position:absolute; 
    left:0; 
    bottom:5px; 
    width:100%; 
    height:3px;                          
    background:#000;
}