The American had struggled to settle in to the Tottenham team, but he helped set up two of the team's goals with an impressive display just behind Defoe.
Villas-Boas is glad Dempsey's on-off move to Liverpool this summer failed to materialise.
"It was a masterclass from our chairman to sign him," Villas-Boas said.
"I gave the green light to do it and I think we did extremely well.
"Sunday was his first full individual 90 minute performance and that was important for him. He has been looking for it to happen for some time."