JSFiddle - React, Tailwind, and code Playground

HTML

<div class="centralizar">
  <div class="central">
    <h1>Olá, estou centralizado!</h1>
  </div>
</div>

CSS

.centralizar {
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  align-items:center;
  justify-content:center;
  
  height: 100vh;
  width: 100%;
  background: #eee;
}
.central {
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  background: #cde;
  padding:24px;
  align-items:center;
}