adobe illustrator - How do I make a radial gradient with "rays" from the origin, not circles?

Learning Illustrator, and I'm trying to find how to make a "radial" gradient that, rather than forming circles around the origin, creates "rays" from the origin:

Example

I've got a similar button design, but can't seem to find the right method. Can't seem to find any tutorials either, but am not entirely sure what to search for.