After Kayani had given Slough an early lead, the Rebels also bounced back from the blow of conceding an equaliser, with Tenconi scoring his first from close range before adding another in the second half.
Davies was forced to shuffle his pack for this match, with centre back Matt Hall pulling out through illness leading to a makeshift defence and no fewer than four recognised forwards in the starting lineup - but his side responded with a superb team performance.
Rhys Forster was soon called into action, pulling off a stunning save to deny Klaidi Lolos after a ball through from Aaron Williams-Bushell.
Minutes later, former Oxford City striker Elliot Benyon – who scored a stunning long-range strike against the Rebels in this fixture last season – was denied by Ben Dudzinski, with his volleyed effort being parried away.
But with a quarter of an hour played, the visitors had the lead as Kayani got the final touch to Matt Lench’s corner kick after Lee Togwell had flicked the ball on.
Ten minutes later, the hosts were level with Zac McEachran’s driven effort from outside the box proving too powerful for Forster to keep out, with the ball hitting the corner of the net.
Slough came straight back and just past the half hour mark, Tenconi put Slough back in front, smashing a loose ball home from barely a yard out after fine work from Ogo Obi down the right.
As half time loomed, Slough let City off the hook with Benyon latching onto a cross at the back post, but the striker could only fire the ball straight at Dudzinski.
But the Rebels were in no mood to let their lead slip in the second period, and minutes after Dudzinski saved a curling effort from Obi, Tenconi had his second goal.
The striker – who will now return to the US to continue his studies after a brief cameo this month – chased a ball forward and was able to head it over the advancing Dudzinski and into the empty net.
City made chances for themselves, with Lolos dragging a shot wide and later seeing another effort saved by Forster after superb work from substitute Alfie Potter down the left.
There was almost a hat-trick for Tenconi, but the striker missed a clear chance with seven minutes remaining.
Slough will now host Oxford City in the return match of the festive double-header at Arbour Park on Sunday afternoon.
Slough Town Line Up
- 1 Rhys Forster
- 6 Lee Togwell
- 8 Matthew Lench
- 9 Ogo Obi 7
- 10 Elliot Benyon
- 12 George Hunt 11
- 14 Scott Davies
- 16 Gabriel George
- 17 Alfonso Tenconi
- 19 Imran Kayani 15
- 20 Aaron Kuhl
Oxford City Line up
Ben Dudzinski, Lewis Miccio, Josh Ashby, Andre Burley, Lewis Coyle (Alfie Potter 56), Reece Fleet (c), Joe Iaciofano (Josh Parker 76), Zac McEachran, Klaidi Lolos, Aaron Williams-Bushell, Canice Carroll. Unused substitutes: Jayden Carbon, Alex Grantham, Latrell Humphrey-Ewers.