JSFiddle - React, Tailwind, and code Playground

HTML

<div>
Hello
</div>

CSS

div
{
   display: inline-block;
   position: relative;    
}
div::before
{
   content: "";
   display: block;
   position: absolute;
   z-index: -1;
   width: 100%;
   height: 100%;
   background:red;
   opacity: .2;

}