Luton exacted quick revenge for their Sky Bet Championship defeat at Cardiff City Stadium earlier in the month as they won 3-0 to reach the third round of the Carabao Cup.
Graeme Jones' side dominated possession with their sweet passing game and Chelsea loanee Izzy Brown stood out in midfield.
But it was the second-half goal from left-back Alan Sheehan that sealed the deal as he bent an unstoppable left-footed free-kick around the Cardiff wall and past the despairing dive of goalkeeper Joe Day in the 62nd minute.
Jones had asked his newly-promoted side to build on the momentum of their first Championship win of the season at Barnsley last weekend and, even with 10 changes to his starting line-up, they were able to do just that.
Sheehan's super strike doubled the lead and then Jake Jervis showed off his power and then precision as he hammered home a third goal in the 69th minute.