<!DOCTYPE html>
<html class="reftest-wait">
<style>
button {
  padding: 0px;
  border:none;
  font-size: 64px;
  background-color: green;
}
button::-moz-focus-inner {
  padding-inline-start: 0px;
  padding-inline-end: 0px;
}
button:-moz-focusring::-moz-focus-inner {
  border: 4px solid;
}
</style>
<div>
  <button id="button1"><span>Menu1</span></button>
</div>
<script>
window.onload = () => {
  button1.focus();
  document.documentElement.classList.remove('reftest-wait');
}
</script>
</html>