<button onclick="window.location.href='https://example.com';">I'm a button with a link</button>

This code from the demo shows, why not using classes to style a website is a misguided idea.

Maybe something like this would be a better idea if you absolutely must avoid classes:

https://jsfiddle.net/qa2cdj4v/

  <strong><a href="#">Button</a></strong>

  strong > a:first-child:last-child {
    display: inline-block;
    background: red;
    color: white;
    padding: 10px;
    font-weight: normal;
  }