<div class="card-title cardtext">
  <p>Header Title</p>
</div>

div
{
  position: relative;
  display: block;

  height: 100px;
  width: 100%;

  background-color: #000;
}

p{
  position: relative;
  display: inline-block;

  background-color: #3d3d3d;
  color: #fff;

  width: auto;
  padding: 0px;
  margin: 0px;

  font-size: 24px;
}