RT Adam Argyle
```css
.hotdog-bun {
border-radius: 50% 50% 100% 0% / 100% 100% 0% 0%;
}
.hamburger-bun {
border-radius: 100vmax 100vmax 0 0;
}
```
the extended syntax for `border-radius` makes it possible for a smooth curve corner to corner (hamburger-bun)
demo
https://codepen.io/argyleink/pen/PoKGJdW

https://twitter.com/argyleink/status/1451173674850013189