JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>
    
<p></p>
    
<span></span>

CSS

div, p, span {
    width: 150px;
    height: 150px;
    background: purple;
    margin: 20px;
    display: block;    
}

div { border-radius: 20px/50px; }
p   { border-radius: 20px/50px 20px/50px 0 0; }
span {
    border-top-left-radius: 20px/50px;
    border-top-right-radius: 20px/50px;
}