Arsenal gifted Tottenham the lead when Bernd Leno spilled the ball straight into the path of Christian Eriksen.
Despite the mistake, Unai Emery is likely to be more frustrated with the second goal.
As Heung-min Son laid the ball off, he was chopped down by Granit Xhaka inside the box.
The Swiss international was late and gave Martin Atkinson no choice but to point to the penalty spot.
Up stepped Harry Kane, who rifled the ball in to make it 2-0.
Sky Sports man Gary Neville couldn’t believe what he was seeing from the midfielder.
“It’s absolute madness from Xhaka,” said Neville during commentary.
“He does it week in, week out. Season after season.
“He doesn’t seem to learn.”
Jamie Redknapp agreed with the former Manchester United defender, claiming it was a rash decision from Xhaka.
“It was a ridiculous tackle to make,” added Redknapp.
Things did get better for Arsenal before the interval, as Alexandre Lacazette rifled the ball into the roof of the net on the stroke of half-time.