JSFiddle - React, Tailwind, and code Playground

HTML

<textarea></textarea>

<div id="source" style="width:80%;background-color:red;">
	Cover <br><br> Me
</div>

CSS

div#source {
    position: relative;
}

div#source:after {
    content: "Covered";
    background: purple;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}