JSFiddle - React, Tailwind, and code Playground

HTML

<div class="position--relative">
    <div class="position--absolute">
        <h1>POSITION THIS TEXT CENTRALLY INSIDE THE CONTAINER</h1>
    </div>
</div>

CSS

.position--absolute {
  background-color: #369;
  height: 300px;
  position: absolute;
  width: 200px;
}

h1 {
  font-size: 13px;
  margin: 0;
  position: relative;
  transform: translateY(-50%);
  top: 50%;
}