This should help. I changed background-color, added width, color, font-weight, and used padding to give you the space. Adjust to your needs.
<div style="height:2px; background-color: #8000FF; text-align: center; width: 200px;">
<span style="margin-right:-5%; margin-left:-5%;background-color: red; color: #fff; font-weight: bold; position: relative; top: -0.5em; padding-right: 10px; padding-left: 10px;">
Lets Begin
</span>
</div>