JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

body{
    background:#eee;
}
div{
    position:absolute;
    width:250px;
    height:50px;
    background:#fff;
    border-radius:0 0 50px 0;
    box-shadow:0 0 20px rgba(0,0,0,.2) 
}
div:after{
    content:'';
    position:absolute;
    height:70px;
    width:70px;
    top:0;
    left: -50px;
    border-radius:100px 0 0 0;
    border: 50px solid #fff;
    background:#eee;
    clip: rect(50px, 100px, 100px, 50px);
    box-shadow:inset 0 0 20px rgba(0,0,0,.2)
}