JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

body{
    background:skyblue;
}

.container{
    height: 100px;
    width: 100px;
    background:red;
    position:relative;
    margin-top:100px;
    margin-left:100px;
}
.shape{
    width: 50px;
    height: 100px;
    top:0px;
    left:-50px;
    overflow:hidden;
    position:absolute;
}
.shape:after{
    content:'';
    width: 100px;
    height: 100px;
    border-radius: 100px;
    background:rgba(0,0,0,0);
    position:absolute;
    top:-40px;
    left:-90px;
    border:40px solid red;
}