Ederson gifted Manchester United two goals and the local bragging rights with a 2-0 win over rivals Manchester City at Old Trafford.
The goalkeeper let Anthony Martial's volley squeeze inside his near post in the first half before kicking the ball straight to Scott McTominay deep into stoppage time for a grandstand finish from distance.
Ole Gunnar Solskjaer reverted to his tried and tested five-man defence, with defender Brandon Williams recalled to the side while Kevin De Bruyne failed to recover from injury in time for City, with Phil Foden starting in his place.
Perhaps unsurprisingly, it was the champions who controlled the early proceedings and had the first chance of the game after 10 minutes. Sergio Aguero capitalised on Luke Shaw's error to play in Raheem Sterling but his curling effort was parried away confidently by David De Gea.
Despite a few defensive wobbles for United, the home side soon settled into their shape and showed their own attacking endeavour, with Daniel James forcing Ederson in a save on the quarter-hour mark.
Martial was looking dangerous too, although the Frenchman was guilty of greed in front of goal, shooting tamely when Bruno Fernandes was a better option. However, the pair combined two minutes later to open the scoring.
City were aggrieved after Fernandes won a dubious foul but the Portuguese showed quick thinking to dink a ball over the top to Martial, who struck his volley at Ederson and it squirmed underneath the Brazilian, who should have done a lot better.
United were confident and attacking with purpose, while City were struggling to retain possession - something unheard of from a Guardiola side.
And the hosts felt they should have had a penalty when Fred went down under a challenge from Nicolas Otamendi. Referee Mike Dean produced a yellow card for simulation, but the replay showed there was definitely contact.
City looked sharper and more aggressive in the second half and if it wasn't for a marginal offside flag against Aguero, could have been level. Alas, VAR agreed with the assistant referee and it remained 1-0.
Ederson's nightmare very nearly plunged into desperation after miscontrolling a passback on his own goal-line, with Martial inches away from getting a foot in.
But City's inevitable improvement arrived around the hour mark and Guardiola refreshed his side with a double change, bringing on Gabriel Jesus and Riyad Mahrez for Aguero and Bernardo Silva.
That appeared to spark some life into City, with Foden moving centrally and getting more involved in the build-up, with Mahrez willing to take on Williams in a one-on-one situation as City ventured forward down the right flank.
Sterling had the chance to get City back on level terms with 12 minutes to go after a pinpoint cross from Mahrez but lost his footing at the vital moment before De Gea produced a fine stop to deny Jesus.
That was the closest they came as United weathered the storm - quite literally as the rain poured down in the final moments - before Ederson cleared the ball straight to McTominay to finish into an empty net from fully 30 yards and clinch a first league double over City for 10 years.
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