<button>Связь с менеджером</button>
<button class="v2">Связь с менеджером</button>
<button class="v3">Связь с менеджером</button>
<button class="v4">Связь с менеджером</button>

body {
  background: #080808 url(https://ns328286.ip-37-187-113.eu/ew/wallpapers/800x480/06547_800x480.jpg) no-repeat;
  background-size: cover;
  padding: 1rem;
}
body::before {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  content: "";
  background: rgba(0, 0, 0, 0.7);
}

button {
  --border-color: rgba(176, 149, 255, 0.92);
  margin: 0.5rem;
  font-size: 30px;
  font-weight: bold;
  text-transform: uppercase;
  color: #fff;
  padding: 1.5rem;
  background: none;
  border-radius: 2rem;
  border: none;
  position: relative;
}

button::before {
  position: absolute;
  content: "";
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(167.1deg, transparent 1.06%, var(--border-color) 92.98%);
  border-radius: 2rem;
  inset: 0;
  -webkit-mask: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg"><rect x="5" y="5" width="calc(100% - 10px)" height="calc(100% - 10px)" rx="1.7rem" ry="1.7rem" fill="black"/></svg>') 0/100% 100%, linear-gradient(#fff, #fff);
  -webkit-mask-composite: destination-out;
  mask: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg"><rect x="5" y="5" width="calc(100% - 10px)" height="calc(100% - 10px)" rx="1.7rem" ry="1.7rem" fill="black"/></svg>') 0/100% 100%, linear-gradient(#fff, #fff);
  mask-composite: exclude;
}

button.v2 {
  --border-color: rgba(255, 0, 0, 0.92);
}

button.v3 {
  --border-color: rgba(0, 255, 0, 0.92);
}

button.v4 {
  --border-color: rgba(14, 190, 255, 0.92);
}