JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div class="button">
  <div class="button__text">Button text</div>
  </div>
</body>
</html>

CSS

body {
  background-color: #222;
}

.button {
  background-color: white;
  padding: 20px;
  border-radius: 40px;
  margin: 40px;
  width: 250px;
  position: relative;
  overflow: hidden;
  transition: all 0.2s;
}

.button::before{
  content: '';
  position: absolute;
  left: -10px;
  top: -10px;
  width: calc(100% + 20px);
  height: calc(100% + 20px);
  background-color: transparent;
  transition: 0.5s;
}

.button__text {
  position: relative;
  z-index: 1;
  color: black;
}

.button:hover::before {
  background-color: black;
}

.button:hover .button__text {
  color: white;
}