<a class="btn" href="#">
  <span>A button!</span>
</a>

body {
  background: #e7e8e9;
  padding: 40px;
}

.btn {
	background-image: linear-gradient(to right, #006175 0%, #00a950 100%);
	border-radius: 40px;
  box-sizing: border-box;
	color: #00a84f;
	display: block;
	font: 1.125rem 'Oswald', Arial, sans-serif; /*18*/
	height: 80px;
	letter-spacing: 1px;
	margin: 0 auto;
	padding: 4px;
	position: relative;
  text-decoration: none;
	text-transform: uppercase;
	width: 264px;
	z-index: 2;
}

.btn:hover {
	color: #fff;
}

.btn span {
	align-items: center;
	background: #e7e8e9;
	border-radius: 40px;
	display: flex;
	justify-content: center;
	height: 100%;
	transition: background .5s ease;
	width: 100%;
}

.btn:hover span {
	background: transparent;
}