• HTML
• CSS

HTML

<div class="container">
    <a href="#">
        <span>Button</span>
    </a>
    <a href="#">
        <span>Button</span>
    </a>
</div>

CSS

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500&display=swap');

*{
    margin:0;
    padding:0;
    box-sizing:border-box;
    font-family:"Poppins",sans-serif;
}
body
{
    display:flex;
    justify-content:center;
    align-items:center;
    min-height:100vh;
    background:#0e1538;
}
.container
{
    display:flex;
    justify-content:center;
    align-items:center;
    flex-direction:column;
}
.container a
{
    position:relative;
    width:160px;
    height:60px;
    display:inline-block;
    background:#fff;
    margin:20px;
}
.container a:before,
.container a:after
{
    content:'';
    position:absolute;
    inset:0;
    background:#f00;
    transition:0.5s;
}
.container a:nth-child(1):before,
.container a:nth-child(1):after
{
    background:linear-gradient(45deg,#00ccff,#0e1538,#0e1538,#d400d4);
}
.container a:nth-child(2):before,
.container a:nth-child(2):after
{
    background:linear-gradient(45deg,#00ccff,#0e1538,#0e1538,#1aff22);
}
.container a:hover:before
{
    inset:-3px;
}
.container a:hover:after
{
    inset:-3px;
    filter:blur(10px);
}
.container a span
{
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:100%;
    display:inline-block;
    background:#0e1538;
    z-index:10;
    display:flex;
    justify-content:center;
    align-items:center;
    font-size:1.2em;
    text-transform:uppercase;
    letter-spacing:2px;
    color:#fff;
    border:1px solid #040a29;
    overflow:hidden;
}
.container a span::before
{
    content:'';
    position:absolute;
    top:0;
    left:-50%;
    width:100%;
    height:100%;
    background:rgba(255,255,255,0.075);
    transform:skew(25deg);
}

/*  Todos los créditos a su autor
    https://www.youtube.com/watch?v=lCxfo8tvHqk
*/