JSFiddle - React, Tailwind, and code Playground

HTML

<div>
</div>

CSS

div {
    height: 200px;
    background: red;
    position: relative;
    width:200px;
}

div:after {
    content: '';
    position: absolute;
    top: -20px; right: -20px;
    border-top: 50px solid white;
    border-left: 50px solid white;
    width: 0;
    background:#fff;
    	border-radius:100px;
        
}
div:before {
    content: '';
    position: absolute;
    top: -20px; left: -20px;
    border-top: 50px solid white;
    border-left: 50px solid white;
    width: 0;
    background:#fff;
    	border-radius:100px;
        
}