How can I paint a sector only with border-radius?

Question

As we know, in CSS, we can use:

width : 100px; height : 100px; border-radius : 100% 0 0 0;

To paint a sector with 90deg; and I want to use this way to paint a sector with any deg. But the front sector doesn't cover perfectly. It leaks a slice of red sector and I don't know how to handle it.

body {
  background-color: #fbb;
}

.box {
  width: 200px;
  height: 200px;
  position: relative;
  background-color: #f00;
  border-radius: 100% 0 0;
}

.box::after {
  content: '';
  display: block;
  position: absolute;
  width: 100%;
  height: 100%;
  background-color: #fbb;
  border-radius: 100% 0 0;
  -webkit-transform-origin: 100% 100%;
  transform-origin: 100% 100%;
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
}

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