JSFiddle - React, Tailwind, and code Playground

HTML

<div class="test"></div>

CSS

.test:before {
    content:"";
    display:block;
    position:absolute;
    top: -15px;
    left: -20px;
    height: 80px;
    width: 50px;
    border-radius: 0 50% 50% 0;
    background-color: #fff;
}
.test {
    position: relative;
    height: 50px;
    width: 50px;
    border-bottom-right-radius: 500% 1000%;
    background-color: #000;
}