JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrap">
    <div id="top"></div>
    <div id="center"></div>
 </div>

CSS

html { height: 100%; }
body { height: 100%; margin: 0; }

#wrap {
    display: flex;
    flex-direction: column;
    height: 100%;
    background-color: lightgray;
    position: relative;
}

#top {
    flex: 0 0 50px;
    width: 100%;
    background-color: orange;
}

#center {
    background-color: aqua;
    width: 200px;
    height: 300px;
    
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}