<a href="#" class="btn">
  <svg width="210" height="60">
    <defs>
        <linearGradient id="grad1">
            <stop offset="0%" stop-color="#F0583A"/>
            <stop offset="100%" stop-color="#F0583A" />
        </linearGradient>
    </defs>
     <rect x="5" y="5" rx="25" fill="none" stroke="url(#grad1)" width="200" height="50"></rect>
  </svg>
    <span>Отправить</span>
</a>

<style>
.btn {
    position: relative;
    display: inline-block;
    width: 210px;
    height: 60px;
    font-size: 1em;
    font-weight: bold;
    line-height: 60px;
    text-align: center;
    text-transform: uppercase;
    background-color: transparent;
    cursor: pointer;
    text-decoration: none;
    font-family: 'TildaSans', sans-serif;
    font-weight: 900;
    font-size: 17px;
    letter-spacing: 0.045em;
}
.btn svg {
    position: absolute;
    top: 0;
    left: 0;
}
.btn svg rect {
    stroke-width: 4;
    stroke-dasharray: 353, 0;
    stroke-dashoffset: 0;
    -webkit-transition: all 600ms ease;
    transition: all 600ms ease;
}
.btn span{
  background: #F0583A;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.btn:hover svg rect {
    stroke-width: 4;
    stroke-dasharray: 132, 543; /*первое значение отвечает за длину нижнего бордера в конце анимации*/
    stroke-dashoffset: 437;
}
</style>