How to slice a cake

This is one of the easier math problems that requires either one good look or several minutes' worth of squinting at it and trying to force your mind to think out of the box.  To many mathematicians, the answer seems obvious as soon as they hear the problem, but for some people, it takes awhile.

How to cut a generic birthday cake into eight pieces in no more than three straight cuts? No special tools or anything.

The answer is at answersdiscarded.blogspot.com.

Please, please, please try to think of the answer before looking it up.