burn at the stake
Execute someone by tying to a stake and burning; also, punish severely. This expression refers to a method used in the Middle Ages for putting heretics to death, but now it is used as a hyperbolic metaphor for harsh punishment, as in She was sure she'd be burned at the stake for losing the contract. In fact, the stake can be used loosely for any extreme punishment. William Makepeace Thackeray so used it in Henry Esmond (1852): "'I know I would go to the stake for you,' said Harry."