JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div{
    display:block;
    width:200px;
    height:200px;
    background:#eee;
    position:relative;
    overflow:hidden;
}
div:after{
    content:'Some text';
    display:block;
    width:200px;
    height:20px;
    position:absolute;
    transform:rotate(45deg);
    background:#f00;
    color:#fff;
    text-align:center;
    line-height:20px;
    right:-50px;
    top:40px;
}