JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="overhang"></div>
    <div id="falloff-shadow"></div>
</div>

CSS

#container { background: #5A5A5A; width: 700px; padding: 200px 0 80px 0px;}
#overhang { background: #5A5A5A; border-top: 1px solid #666; height: 80px; width: 600px; margin: 0 auto; position: relative; z-index: 5;}
#falloff-shadow { width: 500px; margin: 0 auto;
-webkit-box-shadow: 0px 5px 50px 5px rgba(0, 0, 0, 1);
-moz-box-shadow: 0px 5px 50px 5px rgba(0, 0, 0, 1);
box-shadow: 0px 5px 50px 5px rgba(0, 0, 0, 1); 
    position: relative;
    z-index: 1;
    height: 1px;
    top: -65px;
}