HTML Setup

<button class="btn">
    Hover me
</button>

CSS Styles

body {
  background: #111;
}

.btn {
  cursor: pointer;
  background: none;
  border: none;
  color: white;
  border-radius: 100vmax;
  padding: 1rem 2rem;
  position: relative;
}

The Gradient Effect

.btn::before {
  content: "";
  background-image: 
    conic-gradient(
      #fff 0deg, transparent 320deg
    );

  /* Should be bigger than button */
  height: 200px;
  width: 200px;


  /* Centering the gradient  */
  position: absolute;
  top: 50%;
  left: 50%;
  transform: 
      translate(-50%,-50%) 
      rotate(0deg);

  border-radius: inherit;
  transition: 
        transform 1s 
        cubic-bezier(0.3, 1, 0.3, 1);
}

Rotate Gradient on Hover

.btn:hover::before {
  transform: 
        translate(-50%,-50%) 
        rotate(-360deg);
}

Set overflow hidden in the parent element

.btn {
  overflow: hidden;
}

Covering up the gradient

- Here we added btn-content div to cover up the gradient by setting its background color same as the main body color of the page and setting the gradient z-index to -1

<button class="btn">
  <div class="btn-content">
       Hover me
  </div>
</button>

.btn {
  /* Becomes Border Size */
  padding: 3px; 
}

.btn::before {
  /* Put gradient behind btn-content */
  z-index: -1; 
}

.btn-content {
  background: #111;
  padding: 1rem 2rem;
  border-radius: inherit;
}

Here's the Codepen Link

That's it you just learned how to create this awesome hover effect, I hope you found this one helpful and If you have any questions or comments please feel free to leave them below.