The striker did not feature in the first leg due to ankle ligament damage that he suffered against Manchester United in January, but he has now scored three goals in four appearances since his return to the pitch.
The 25-year-old's 49th-minute run split the hosts' centre-backs, as he latched onto Moussa Sissoko's pass and curled a shot past Dortmund goalkeeper Roman Burki.
Dortmund then put the Tottenham defence under an intense siege but Hugo Lloris saved a Julian Weigl drive, Ben Davies blocked the follow-up attempt and, in what seemed a mere heartbeat, Davinson Sanchez deflected a thunderous Reus drive behind. "You can not hope to score five". It was unlucky for us.
"This is a huge step, but we have to keep growing and we need more nights like this", Kane said.
His blistering pace saw him succeed as a winger at times to terrorise full-backs, while he was also effective in a more central role alongside Harry Kane. "A player every team would love to have".
"To move to the next level or the last level, I think it is not only today to show a very professional performance", Pochettino told reporters.
"I think that is not fair and it is a problem that in the future it is a thing we need to change if we want to help the English clubs be stronger in the competition. Of course that is only we are going to be in the Champions League quarter-finals but it's a fantastic achievement for the team".
"The plan was different but during the game what happened happened and we needed to adapt ourselves", said Pochettino. Lloris was magnificent tonight. Join me for all the latest team news, match commentary and Goals as they go in!
"The mentality was good and I'm so happy for the players and the fans". "I was talking yesterday with Daniel [Levy, the chairman] and he was very positive. They live for those moments".