<button href="#" class="grow_ellipse">Кнопка</button>

<style>
button {
    width: 202px;
    height: 50px;
    font-size: 24px;
    background: #f0583a;
    color: #ffffff;
    border: 4px solid #f0583a;
    border-radius: 40px;
    padding: 0;
    position: relative;
    z-index: 1;
    overflow: hidden;
}
button:hover {
    color: #f0583a;
}
button::after {
    content: "";
    background: #ffffff;
    position: absolute;
    z-index: -1;
    display: block;
}
button.grow_ellipse::after {
    border-radius: 46%;
    left: -50%;
    right: -50%;
    top: -150%;
    bottom: -150%;
    transform: scale(0, 0);
    transition: all 0.3s ease;
}
button.grow_ellipse:hover::after {
    transform: scale(1, 1);
    transition: all 0.9s ease-out;
}
</style>