Chelsea striker Diego Costa was shown the red card, following Lukaku's five-minute double, for a second booking as he retaliated with face-to-face aggression after being fouled by Gareth Barry.
Barry was then given a second yellow card three minutes from time but Lukaku, sold by former Chelsea manager Jose Mourinho to Everton for 28 million pounds ($40.28 million) two years ago, had already put victory beyond doubt.
With a replay looking likely, Lukaku conjured up a goal from nowhere, muscling past two defenders on the left flank, powering into the box and, after some nifty footwork, firing a left-foot shot into the corner.
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It ended Premier League champions Chelsea's chances of any silverware at the end of another wretched week that also saw them crash out of the Champions League against Paris St Germain.
And it meant caretaker manager Guus Hiddink, who won the FA Cup seven years ago in his previous stand-in spell at Stamford Bridge, had failed in his bid to repeat the achievement following the dismissal of Mourinho in December.
(Reporting by Ian Chadband; Editing by Tony Jimenez)
