JSFiddle - React, Tailwind, and code Playground

HTML

<div id="circle"></div>

CSS

#circle { 
   width: 400px;
   height: 400px;
   background: green; 
   -moz-border-radius: 200px; 
   -webkit-border-radius: 200px; 
   border-radius: 200px;
    position: relative;
}
#circle:before{
    display: block;
    content: '';
    width: 100px;
    height: 100px;
    background: white; 
    -moz-border-radius: 50px; 
    -webkit-border-radius: 50px; 
    border-radius: 50px;    
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    
}