Semenyo scored from a corner, but Erling Haaland was deemed to be in an offside position, grappling with a Newcastle defender near the goal line.
VAR officials spent over four minutes reviewing the incident, using superimposed lines to determine Haaland was a toe further forward than defender Malick Thiaw.
Referee Chris Kavanagh was called to the pitchside monitor and ultimately ruled that Haaland was impacting the defender's ability to play the ball from an offside position.
The decision, announced to the stadium, led to loud cheers from Newcastle fans and reignited discussions about the impact of VAR on the flow of football matches.