JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class="semi-circle"></div>
</body>

CSS

.semi-circle{
    width :200px;
    height:100px;
    background :blue;
    -moz-border-radius: 100px;
    -webkit-border-radius: 100px;
    border-radius: 100px 100px 0 0;
}