Изогнутый фон блока сверху и снизу

.violet-section {
  background: radial-gradient(95.07% 139.28% at 50% -43.54%, #513E63 0%, #282837 29.64%, #4D4793 85.3%, #9260A9 100%);
  height: 248px;
  margin-bottom: 150px;
  border-radius: 0 0 50% 50% / 0 0 40px 40px
 }
 
 

<div class="violet-section"></div>