JSFiddle - React, Tailwind, and code Playground

HTML

<div style="" class="tt"></div>

CSS

.tt {
  width:500px;
  height:400px;
  border:1px solid red
}

.tt::before {
  background-color: #000;
  content: "";  
  position: absolute;
  top: 0;  
  width: 500px;
  height: 200px;
  z-index: -1;  
}