Lacazette, captaining the Gunners after Pierre-Emerick Aubameyang had been withdrawn from the team following a breach of pre-match protocols, converted a 64th-minute spot-kick to secure a 2-1 fightback win.
Emile Smith Rowe was unfortunate not to open his league account when his 16th-minute effort came back off the crossbar with Hugo Lloris beaten, and substitute Lamela, on for the injured Son Heung-min, took full advantage with an audacious rabona finish from Lucas Moura’s lay-off 12 minutes before the break.
Full-back Cedric Soares saw his 37th-minute piledriver crash against the upright as the Gunners responded, but they were back in it with a minute of the first half remaining when Martin Odegaard’s shot clipped defender Toby Alderweireld and eluded Lloris.
Lacazette put the home side ahead from the spot after being felled by Davinson Sanchez’s untidy challenge before Lamela was dismissed for a second bookable offence.
Harry Kane had a late header ruled out for offside and then rattled a post with an 89th-minute free-kick in a tense conclusion to the game.
Arsenal player ratings
Simon Collings handed out four 8/10s for the Gunners today.
Mourinho goes in on referee again
Mourinho, who bemoaned the lack of post-match interviews for officials, admitted his team had not been good enough before the break.
He said: “I think we played really badly in the first half. The 1-1 was not a fair reflection of the first half. We were poor, defending badly, no intensity, no pressing, even in terms of creating attacking football, some important players hiding. The first half was really bad.
“In the second half, we only had space to improve; we did and then it’s a question for – it’s an impossible question because they don’t speak – but a question for Michael to answer, and probably Paul Tierney too because he was the VAR.
“But, according to Kevin Friend, the referee said he had a clear vision and the VAR didn’t want to go against.”
Mourinho: Penalty a ‘mistake’ by referee
Spurs boss Mourinho was unhappy with the penalty decision which ultimately cost his side.
He told Sky Sports: “It was a mistake by (referee) Michael Oliver. Players get tired – there are so many matches – coaches get tired, referees, maybe they get tired. He had a game midweek I don’t know, Champions League or Europa League, maybe tired.
“Normally I am very unlucky with him because my record with him on penalties is astonishing with Chelsea, United, Tottenham. It doesn’t matter which club, I am very, very unlucky with such a good referee.”
Arteta explains Aubameyang absence
Asked why he had to take such firm action with Aubameyang, Arteta, who declined to confirm that the player had been dropped for being late, said: “Because we have a way of living together, that we have to respect each other and that’s it.
“But he’s an incredible guy, he’s probably one of the most important players in the team, he’s our captain.
“These things happen. We move forward. Let’s enjoy the victory tonight and let’s dedicate it to our fans.
“These things happen in football. There are a lot of things going on in our lives, people are finding it really difficult to handle all the restrictions that we have as well. It’s part of our job.”
Arteta: Arsenal reacted with ‘a lot of personality’
Gunners boss Arteta praised his players for the way they responded to adversity.
Asked how much credit they deserved, Arteta told Sky Sports: “Full credit, to do it the way we did it today after two-and-a-half days coming back from Europe, to play with the intensity, to show the quality that we did.
“The spirit that we showed throughout the game was incredible, going 1-0 down after the way we were playing was really disappointing and probably the worst-case scenario for us to play against a team like Spurs.
“But we reacted with a lot of personality, we kept playing and I think we deserved the win.”
More penalty debate
Ljungberg was in agreement with Dawson.
He said: “They (Arsenal) were a bit lucky. If I came with the ball down at my feet and I dribble, I get a tackle from the inside, I shoot into the heel of the defender and I get a shot off, I will not get a penalty for that.
“I think they’re very lucky to get this penalty.”
Was it a penalty?
Former Spurs defender Michael Dawson, working as a pundit for Sky Sports, was not convinced the penalty should have been awarded.
He said: “When Lacazette makes that touch, he just gives Sanchez a little opportunity. Sanchez goes to make the block and because the ball is high up, you think does Lacazette kick Sanchez?
“What else can Sanchez do unless he lets him shoot? As soon as he comes across, he makes that block, but I think Lacazette kicks him.
“The only thing is it’s reckless and high, but the ball is bouncing. Sanchez comes, yes, probably slightly too late, but Lacazette touches the ball first and it has gone away. If he nudges it, I’m still not sure.”
Lacazette: Finale ‘really stressful’
Asked how stressful the last 10 minutes had been as he watched from the bench, Lacazette added: “It’s really stressful because this is our problem when we are winning. We had some problems to manage the game at the end, even 11 v 10. This is where we have to improve a lot.
“But at the end, we won, we need to appreciate the three points and think about Thursday.”
Match-winner Lacazette was thrilled with the victory.
He told Sky Sports: “It’s amazing. We wanted to win this game for us, for the team and as well for the fans. I think they’re happy, even if we missed them today in the stadium, but it was really important for us to win the derby.”
Davinson Sanchez is not happy at full-time – he is arguing with referee Michael Oliver, but it won’t do any good now.