Button with transparent background and rotating gradient border

Question

What I'm trying to achieve is a button like

Once it's done I need to animate on hover. The closest example I could find is this codepen

https://codepen.io/Chester/pen/QPoyjN

The problem is the ::after that is required to apply a white background on the button

The size of the button might change based on the text length so a solution like the one given here is not valid : Rotate only the Border using CSS

Here's what I got so far, the goal is to keep a similar animation but remove the white background

.background {
  width: 600px;
  height: 600px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-image: url("https://via.placeholder.com/600");
}

.button-file {
  display: block;
  position: relative;
  text-align: center;
  z-index: 0;
  border-radius: 30px;
  max-width: 363px;
  max-height: 46px;
  border-radius: 30px;
  overflow: hidden;
  padding: 1rem 2rem;
}

.button-file::before {
  content: '';
  position: absolute;
  z-index: -2;
  left: 50%;
  top: 50%;
  width: 400px;
  height: 400px;
  border-radius: 30px;
  background-repeat: no-repeat;
  background-size: 50% 50%, 50% 50%;
  background-position: 0 0, 100% 0, 100% 100%, 0 100%;
  background-image: linear-gradient(#44a0b0, #44a0b0), linear-gradient(#44a0b0, #44a0b0), linear-gradient(#eeb450, #eeb450), linear-gradient(#eeb450, #eeb450);
  transform: translate(-50%, -50%) rotate(11deg);
  transition: transform .7s cubic-bezier(1, 0, 0, 1);
}

.button-file:hover::before {
  transform: translate(-50%, -50%) rotate(191deg);
}

.button-file::after {
  content: '';
  position: absolute;
  z-index: -1;
  left: 3px;
  top: 3px;
  width: calc(100% - 6px);
  height: calc(100% - 6px);
  background: #fff;
  border-radius: 30px;
}

<div class="background">

  <div class="button-file">
    <a>En savoir +</a>
  </div>

</div>

Answer 1

With mask you can do it

.button-file {
  position: relative;
  overflow:hidden;
  color: #fff;
  z-index: 0;
  padding: 1rem 2rem;
}

.button-file i {
  content: '';
  position: absolute;
  z-index: -1;
  inset: 0;
  border-radius: 30px;
  padding: 5px; /* the thickness of the border */
  /* the below will do the magic */
  -webkit-mask: 
     linear-gradient(#fff 0 0) content-box, /* this will cover only the content area (no padding) */ 
     linear-gradient(#fff 0 0); /* this will cover all the area */
  -webkit-mask-composite: xor; /* needed for old browsers until the below is more supported */
  mask-composite: exclude; /* this will exclude the first layer from the second so only the padding area will be kept visible */
}

.button-file i::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 50%;
  width: 400px;
  height: 400px;
  background: linear-gradient(#44a0b0 50%, #eeb450 0);
  transform: translate(-50%, -50%) rotate(45deg);
  transition: transform .7s linear;
}

.button-file:hover i::before {
  transform: translate(-50%, -50%) rotate(315deg);
}

body {
  height: 100vh;
  margin:0;
  display: flex;
  align-items: center;
  justify-content: center;
  background-image: linear-gradient(to right, blue, red);
}

<a class="button-file">
  <i></i> <!-- an extra element here  -->
  En savoir +
</a>