JSFiddle - React, Tailwind, and code Playground

HTML

<div class="holder">
    <iframe class="frame" />
    <div class="bar"></div>
</div>

CSS

.holder{
    width: 400px;
    height:300px;
    position:relative;
}
.frame{
    width: 100%;
    height:100%;
    background blue;
}
.bar{
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:40px;
    background: red;