JSFiddle - React, Tailwind, and code Playground

HTML

<div id="cont">
    <div id="main">
        <h1>TEST</h1>
    </div> 
</div>

CSS

#cont {
  background: #ddd;
}
#main {
  width: 300px;
  background: #fff;
  margin-left: auto;
  margin-right: auto;
}