.wp-block-button__link {
    border-radius: 0;
    background-color: #6A1BC4;
    padding: .5em 1em .5em 1em;
    color: #fff;
}

.wp-block-button__link:hover {
    background-color: #480693;
}

.wp-block-button__link:visited {
    color: #fff;
}