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

.box {
  --b: 5px;
  --f: 1;
  
  width: 200px;
  aspect-ratio: 1;
  background: 
    radial-gradient(
      circle closest-side,
      #ECD078 calc(99% - var(--b)),#C02942 calc(100% - var(--b)) 99%,lightblue
     ) 50%/calc(100%/var(--f)) 100% no-repeat;
  transform: scale(var(--f));
  cursor: pointer;
  outline: 2px solid green;
  transition: .3s ;
}
.box:hover {
  --f: 1.35;
}

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