HTMLify

*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    min-height: 100vh;
    display: grid;
    place-items: center;
    background: #151515;
}

.button {
    display: inline-block;
    padding: 1rem 2rem;
    border-radius: 10rem;
    background-color: #ff4646;
    color: #fff;

    font-family: Arial;
    font-size: 1rem;
    letter-spacing: 0.15rem;
    text-decoration: none;
    text-transform: uppercase;

    transition: all 0.3s;
    position: relative;
    overflow: hidden;
    z-index: 1;
}

.button::after {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 100%;
    background: #fff;
    z-index: -1;
    border-radius: 10rem;
    transition: 0.3s ease all;
    transform: scale(0, 1);
    transform-origin: top right;
    transition: transform 500ms cubic-bezier(0.86, 0, 0.07, 1);
    transition-timing-function: cubic-bezier(0.86, 0, 0.07, 1);
}

.button:hover {
    color: #151515;
}

.button:hover::after {
    transform: scale(1, 1);
    transform-origin: top left;
}