JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

body {
    background: #1e66ed
}
div {
    -webkit-border-top-left-radius: 40% 80px;
    -webkit-border-top-right-radius: 40% 80px;
    -moz-border-radius-topleft: 40% 80px;
    -moz-border-radius-topright: 40% 80px;
    border-top-left-radius: 40% 80px;
    border-top-right-radius: 40% 80px;
    
    background: #fff;
    height: 280px
}