Claire Allen, 36, said she was the first to notice the image on the underside of the lid as she was putting the yeast spread on her son's toast.
Her husband Gareth, 37, said he could not believe his eyes when he saw it.
Mr Allen, of Ystrad, Rhondda, said: "The kids are still eating it, but we kept the lid."
He explained: "Claire saw it first and called her dad to come and take a photo of it.
"When I first looked at it I wasn't sure, but when I moved it away from me it started coming out. I thought yeah, she's right - that's the image of