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

.box {
  --s: 280px; /* image size */
  --b: 5px;   /* border thickness */
  --c: #C02942; /* border color */
  --f: 1;     /* initial scale */
  
  width: 280px;
  aspect-ratio: 1;
  border-radius: 0 0 999px 999px;
  outline: var(--b) solid green;
  outline-offset: calc((1/var(--f) - 1)*var(--s)/2);
  background: 
    radial-gradient(
      circle closest-side,
      #ECD078 calc(99% - var(--b)),var(--c) calc(100% - var(--b)) 99%,#0000
     ) 50%/calc(100%/var(--f)) 100% no-repeat, lightblue;
  transform: scale(var(--f));
  cursor: pointer;
  transition: .3s ;
}
.box:hover {
  --f: 1.35;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-content: center;
  background: #E0E4CC;
}