Erling Haaland converted a historic penalty to give Manchester City the lead 26 minutes into Sunday's derby clash with Manchester United.
City had never previously been awarded a spot-kick at Old Trafford in the Premier League.
But that changed following a VAR review which resulted in Rasmus Hojlund being punished for grabbing City midfielder Rodri inside the 18-yard box.
Onana had saved a spot-kick in United's 1-0 win over Copenhagen on Tuesday but he got nowhere near Haaland's strike after diving the wrong way.
This was the fourth Manchester derby goal of Haaland's career - after he netted a hat-trick in a 6-3 win at the Etihad Stadium last season.
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