Leaders Celtic returned to form in the Scottish Premier League with a ruthless attacking display against Hearts.
Lassad gave them an early lead, beating Jamie MacDonald at his near post.
As Hearts passed up chances, Celtic extended their lead through Mikael Lustig's close-range strike and a Ryan Stevenson own goal.
Gary Hooper added a late fourth and Fraser Forster rounded off a fine individual performance by saving a Marius Zaliukas penalty.
The atmosphere inside Tynecastle was typically electric for such an occasion from the outset and the visitors' brighter start reflected their noisier support.
MacDonald had already saved a point-blank Kris Commons effort before Celtic took a 10th-minute lead in splendid fashion.
Beram Kayal spread the ball wide to the left and when Kris Commons curled a cross deep to the back post, Lassad swept a composed volley past the keeper.
Forster capped a superb display with a penalty save
Celtic had been showing none of the lackadaisical play that has often afflicted them in the SPL this season, but their defence went to sleep as Hearts should have recorded a swift response.
Stevenson swung a free-kick seemingly onto the head of the unmarked Callum Paterson, but the striker somehow contrived to miss the ball.
The cost of that miss was laid bare with 22 minutes gone as Celtic produced another slick passing move - this time down the right - and though Hearts repelled the initial danger, Lustig pounced on the loose ball to knock past MacDonald.
As formidable as Celtic were looking on the front foot, they still required the excellence of Fraser Forster to maintain their two-goal lead.
The England-squad keeper pushed away a ferocious Stevenson free-kick but it was his reaction to spring up and keep out Marius Zaliukas's header on the rebound that was truly impressive.
Hearts were competing doggedly but found themselves three goals down as the half-hour ticked by.
Charlie Mulgrew showed great appetite to prevent a loose ball from crossing the goal-line, firing it across goal and Stevenson, in his desperation to block, succeeded only in diverting it past MacDonald and into the net.
Hearts could justifiably argue that reflected harshly on the balance of play, but Celtic had delivered a masterclass in clinical finishing.
The home side again had cause to wonder what they had to do to score as Forster pulled off another fabulous save at the beginning of the second half, getting down to his right to turn a Kevin McHattie free-kick round the post.
The second period was unsurprisingly less frenetic than the first, with Hearts unable to make a significant impression on the Celtic rearguard.
They did claim for a penalty - not for the first time in the match - when the ball bounced up onto the arm of Efe Ambrose, but referee Willie Collum adjudged it not to have been deliberate.
That was with just over a quarter-of-an-hour to play and shortly afterwards the Hearts substitute Mehdi Taouil volleyed into the arms of Forster.
As full-time approached, MacDonald saved well from Commons, but as the ball was played back into the box by Mulgrew, Hooper couldn't miss from inside the six-yard box.
Hearts were handed an opportunity to notch a consolation goal from the penalty spot when Kelvin Wilson brought down Stevenson, but the impeccable Forster guessed correctly to save Zaliukas's spot-kick.
Unfair challenge on Marius Zaliukas by Beram Kayal results in a free kick.
Scott Robinson has an effort at goal from long range that misses to the right of the goal.
Short corner worked by Andrew Driver, clearance by Victor Wanyama.
The referee blows for offside. Jamie MacDonald takes the free kick.
Inswinging corner taken from the right by-line by Andrew Driver.
Mehdi Taouil produces a volleyed right-footed shot from 18 yards. Save by Fraser Forster.
Outswinging corner taken left-footed by Andrew Driver, clearance made by Kelvin Wilson.
Booking Callum Paterson goes into the book for dissent.
Substitution Scott Brown on for Joe Ledley.
Substitution Adam Matthews joins the action as a substitute, replacing Mikael Lustig.
Substitution Andrew Driver on for Jamie Walker.
Victor Wanyama has an effort at goal from long distance that misses to the right of the goal.
Substitution Dylan McGowan leaves the field to be replaced by Scott Robinson.
Kris Commons fouled by Dylan McGowan, the ref awards a free kick. Free kick taken by Charlie Mulgrew.
Lassad Nouioui takes a shot. Save by Jamie MacDonald.
Shot by Kris Commons from just outside the area goes over the net.
Direct free kick taken by Charlie Mulgrew.
Substitution Jason Holt leaves the field to be replaced by Mehdi Taouil.
Free kick awarded for an unfair challenge on Kris Commons by Darren Barr.
The assistant referee flags for offside against Lassad Nouioui. Jamie MacDonald takes the indirect free kick.
Free kick awarded for an unfair challenge on Mikael Lustig by Ryan Stevenson. Fraser Forster takes the free kick.
Kelvin Wilson challenges Jason Holt unfairly and gives away a free kick. Strike comes in from Kevin McHattie from the free kick, save by Fraser Forster. Inswinging corner taken from the left by-line by Kevin McHattie, clearance made by Victor Wanyama. Dylan McGowan takes a shot. Blocked by Efe Ambrose.
Corner taken by Kevin McHattie, Fraser Forster makes a save.
The referee starts the second half.
45:00 +0:02 Half time
Half Time The first half comes to an end.
Ryan McGowan challenges Victor Wanyama unfairly and gives away a free kick. Fraser Forster restarts play with the free kick.
Joe Ledley is ruled offside. Jamie MacDonald restarts play with the free kick.
Unfair challenge on Kris Commons by Ryan McGowan results in a free kick. Strike comes in from Charlie Mulgrew from the free kick, clearance by Andy Webster.
Foul by Andy Webster on Lassad Nouioui, free kick awarded. Charlie Mulgrew restarts play with the free kick.
Jason Holt takes a shot. Save made by Fraser Forster.
Kevin McHattie produces a shot on goal direct from the free kick, save by Fraser Forster.
Booking The referee cautions Victor Wanyama for unsporting behaviour.
Foul by Victor Wanyama on Jamie Walker, free kick awarded.
Ryan McGowan fouled by Beram Kayal, the ref awards a free kick. Direct free kick taken by Andy Webster.
Direct strike on goal from the free kick comes in from Ryan Stevenson.
Booking Efe Ambrose is given a yellow card.
Unfair challenge on Jamie Walker by Efe Ambrose results in a free kick.
29:57 Goal scored
Goal! - Ryan Stevenson - Hearts 0 - 3 Celtic Ryan Stevenson concedes an unfortunate own goal. Hearts 0-3 Celtic.
Victor Wanyama gives away a free kick for an unfair challenge on Ryan Stevenson. Ryan Stevenson produces a strike on goal direct from the free kick, save by Fraser Forster.
Beram Kayal concedes a free kick for a foul on Jamie Walker. Direct free kick taken by Kevin McHattie.
Free kick awarded for a foul by Kris Commons on Callum Paterson. Direct effort from the free kick comes in from Ryan Stevenson, fantastic save by Fraser Forster. Marius Zaliukas takes a shot. Save made by Fraser Forster. Ryan McGowan produces a right-footed shot from deep inside the six-yard box which goes wide of the right-hand post.
21:26 Goal scored
Goal! - Mikael Lustig - Hearts 0 - 2 Celtic Mikael Lustig scores a goal from close range to the bottom left corner of the goal. Hearts 0-2 Celtic.
Shot on goal by Charlie Mulgrew from just inside the area clears the crossbar.
Foul by Joe Ledley on Ryan McGowan, free kick awarded. Ryan Stevenson restarts play with the free kick.
Jamie Walker concedes a free kick for a foul on Charlie Mulgrew. Direct free kick taken by Kris Commons.
Kelvin Wilson fouled by Kevin McHattie, the ref awards a free kick. Direct free kick taken by Fraser Forster.
Joe Ledley concedes a free kick for a foul on Jamie Walker. Direct effort from the free kick comes in from Ryan Stevenson.
Kelvin Wilson challenges Ryan McGowan unfairly and gives away a free kick. Kevin McHattie produces a shot on goal direct from the free kick, clearance by Charlie Mulgrew.
The assist for the goal came from Kris Commons.
9:17 Goal scored
Goal! - Lassad Nouioui - Hearts 0 - 1 Celtic Lassad Nouioui gets on the score sheet with a goal from just inside the penalty area to the bottom left corner of the goal. Hearts 0-1 Celtic.
Corner taken by Jamie Walker from the right by-line played to the near post, clearance by Gary Hooper. Outswinging corner taken from the right by-line by Jamie Walker. Free kick awarded for a foul by Kelvin Wilson on Callum Paterson. Andy Webster takes the direct free kick.
Kris Commons takes a shot. Save by Jamie MacDonald.
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