The traditional French phrase to utter when you serve the food is bon appétit: “good appetite” (and pronounced “bone ah-puh-TEE”). It implies “may you enjoy your food with a good appetite.” (For some reason I think this is fine but get irritated when a waiter tells me “enjoy!”)

You see all sorts of misspellings of this phrase: “bon a petite,” “bon à petite,” “bon á petite,” “bona petite,” “bonapetite,” “bon a petit,” etc. All of these are bon à rien—good for nothing.