JSFiddle - React, Tailwind, and code Playground

HTML

<div><span></span></div>

CSS

div {
    border: 5px solid yellow;
    position: relative;
    width: 200px;
    height: 200px;
    margin: 40px auto;
}

span {
    position: absolute;
    left: 0px;
    right: 0px;
    top: 0px;
    bottom: 0px;
    background: aqua;
}