index.html

<div class="reboot">
  <div class="reboot-interior"></div>  
</div>

style.css

.reboot{
  position:relative;
  width: 150px;
  height: 150px;
  display:block;
  border-radius: 100%;
  background: #f9c000;
  background: linear-gradient(top, #f9d900, #f9c000);
  margin: 60px auto;
  box-shadow:0px 2px 5px 0px rgba(0, 0, 0, 1);
  transform: rotate(0deg);
}
.reboot:after{
  content:'';
  position: absolute;
  height: 75px;
  width: 150px;
  display:block;
  top:75px;
  border-radius: 0 0 150px 150px;
  background: #000;
  background: linear-gradient(bottom, #2b2b2b, #000 );
  transform: rotate(0deg);
}
.reboot-interior { 
  position: absolute;
   width: 0; 
   height: 0;
   top: 14px;
   left: 15px;
   border-bottom: 60px solid #000; 
   border-left: 60px solid transparent; 
   border-right: 60px solid transparent;
}
.reboot-interior:after{
   content: '';
   position: absolute;
   z-index: 999;
   width: 0; 
   height: 0;
   top: 60px;
   left: -60px;
   border-top: 60px solid #f8cb04; 
   border-left: 60px solid transparent; 
   border-right: 60px solid transparent;
  transform: rotate(0deg);
}