JSFiddle - React, Tailwind, and code Playground

HTML

<div id="lightbox-border">
    <div id="lightbox">
        <a>Content here.</a>Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.</div>
    <div id="lightbox">
        Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.Content here.
    </div>
</div>

CSS

body {
    margin:50px;
    background-color:green;
}

#lightbox-border {
    background: rgba(0, 0, 0, 0.3);
    padding: 20px; /* This is somewhat the border */
    border-radius: 15px;
}

#lightbox {
    background-color: white;
    
    border-radius: 10px;
    padding: 30px;
}