ずらした枠線と背景色

HTML

<a href="">私たちについて</a>

CSS

a {
  display: block;
  position: relative;
  padding: 30px 10px;
  width: 260px;
  color: #333;
  font-size: 18px;
  font-weight: 700;
  text-align: center;
  text-decoration: none;
  background-color: #90be70;
}

a::before {
  content: '';
  position: absolute;
  top: -8px;
  left: -8px;
  width: calc(100% - 4px);
  height: calc(100% - 4px);
  background-color: rgba(0 0 0 / 0);
  border: 2px solid #2b550e;
}