The Italian stepped up to bend a sublime set-piece past Luis Robles after Daniel Royer had netted a controversial penalty to cancel out Victor Vazquez’s opening goal.
The win gives Toronto a clear advantage going into the second leg but came at a cost, with Drew Moor and Vazquez both substituted with injuries. The defender’s looked the more serious of the two.
After a high-tempo start, TFC struck first. Jozy Altidore stepped around Damien Perrinelle on the right-hand side and saw his low cross pushed into the path of Vazquez by Robles, allowing the Spaniard to curl into the bottom corner.
The difference from last year? He has already stepped up. Victor Vazquez 1-0. pic.twitter.com/GponsE8rY7— Waking the Red (@WakingtheRed) October 30, 2017
The hosts were reeling for most of the rest of the half thereafter, with Altidore having his way with whatever defender he liked and a superb Vazquez cross headed on to the crossbar by Marky Delgado.
But they were reeled back in on the stroke of half-time. Moor was harshly penalized for a challenge on Bradley Wright-Phillips in the box and injured himself in the process, with Royer converting the spot kick and Nick Hagglund replacing Moor during the interval.
The Red Bulls came back out reinvigorated and enjoyed their best spell of the game - a period in which TFC were not aided by a groin injury suffered by Vazquez, who would attempt to hobble on before being brought off for Jonathan Osorio.
Hagglund and Alex Bono especially, though, stood firm in the face of the pressure and Toronto came out unscathed on the scoresheet.
Then Giovinco made them pay.
Wright-Phillips came closest to drawing the Red Bulls level again, but the Englishman was thwarted by Chris Mavinga.
Mavinga would get his fair share of kicks himself before time was out but he survived the physical treatment and TFC the last bit of New York pressure to secure an excellent result.