JSFiddle - React, Tailwind, and code Playground

HTML

<div class='shape'></div>

CSS

.shape{
    height: 100px;
    width: 200px;
    background: red;
    margin-left: 50px;
}
.shape:before{
    position: absolute;
    content: '';
    height: 100px;
    width: 100px;
    background: white;
    border-radius: 50px;
    margin-left: -50px;
}