I think you could make some hay with, say, a cook who has a grudge against the person or family she's working for and starts cleverly mixing up some food issues for punishment. ("I'll show them. I'll cut the vegetables with the same knife I used to I cut the chicken.") But even as that story starts to take shape, I'm thinking that they'll probably show symptoms of food poisoning first, have it diagnosed, and fire the cook. But, sure, she wants to make them sick, but someone dies.
Undercooked food would be a really chancy choice to kill someone intentionally. Anything's possible, but I'm not sure how that would be framed compellingly for the reader.