<div class="wrapper">
  <a href="#"><span>Hover Me!</span></a>
</div>

.wrapper{
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

a{
  display: block;
  width: 200px;
  height: 40px;
  line-height: 40px;
  font-size: 18px;
  font-family: sans-serif;
  text-decoration: none;
  color: #333;
  border: 2px solid #333;
  letter-spacing: 2px;
  text-align: center;
  position: relative;
  transition: all .35s;
}

a span{
  position: relative;
  z-index: 2;
}

a:after{
  position: absolute;
  content: "";
  top: 0;
  left: 0;
  width: 0;
  height: 100%;
  background: #ff003b;
  transition: all .35s;
}

a:hover{
  color: #fff;
}

a:hover:after{
  width: 100%;
}