Real took a giant stride towards the semi-final of Europe's premier club competition by brushing aside last season's runners-up in the quarter-final first leg on Wednesday.
World-record signing Gareth Bale opened the scoring after just two minutes and Isco double Real's lead before half-time.
Cristiano Ronaldo then took centre stage in the second half, equalling Lionel Messi's record of 14 Champions League goals in a season and taking his incredible overall tally for this term to 45.
Dortmund knocked Real out of the competition at the semi-final stage last season, but Jurgen Klopp's side will need a stunning fightback to reach the last four again when the two sides meet in the second leg at Signal Iduna Park next Tuesday.
And goalkeeper Weidenfeller was left to rue the manner in which his side were taken apart by the nine-time European Cup winners.
"We lacked concentration at the start of the game and didn't defend the way we had anticipated," he said.
"At times we made it far too easy for Real. You have to play with confidence here, otherwise you don’t have a chance."
Midfielder Nuri Sahin echoed Weidenfeller's comments and felt that the visitors should have been more clinical.
He said: "We had a lot of counter-attacks and should have scored at least one goal, maybe even two or three. We weren't clever enough in order to get a result here. You don't get a lot of chances against Real."
