I read this one in a magazine. Still cracks me up.
A lady had given her cookie recipe to a neighbor. One day she gets a call from the neighbor that she was making the cookies but the dough just doesn't seem right. The lady went next door and instead of the normal dough, she found a runny mess that had chunky green bits in it.
Confused, she asked the neighbor what happened. The explanation:
"I didn't have cream of tartar, so I substituted tartar sauce."
Ewwwwwwwww ROFL