<div class="box"></div>

.box {
  height: 200px;
  background: red;
  margin: 10px;
  padding-top: 70px;
  /* curved edge at the bottom */
  mask: radial-gradient(80% 100% at 50% -78%,#0000 calc(100% - 2px),#000);
  /* rounded edge at the top */
  clip-path: ellipse(80% 100% at top);
}