JSFiddle - React, Tailwind, and code Playground

HTML

<div class="z1">
  <div class="z2"></div>
</div>

CSS

.z1, .z2 {width:200px;height:200px;}
.z1 {background-color: rgba(1, 1, 1, 0.8);}
.z2 {position:absolute;top:100px;left:100px;background: #000;
opacity: 0.5;}