The 18-year-old started the Europa League last-16 first-leg tie against Dortmund away from home at Signal Iduna Park on Thursday evening.
The youngster played for the entire 90 minutes, as the North London outfit went down 3-0. Onomah, who is very highly rated, has revealed the advice he was given by Pochettino ahead of the match.
“It was a very big night for me,” the England Under-19 international midfielder told Tottenham’s official website. “I was buzzing when I found out that I was starting.
“The gaffer spoke to me beforehand and told me to be confident and I thank him for giving me a chance – it's the biggest stage I've played on.”
Onomah has got his chances this season and has been quite impressive whenever he has played.
In seven Premier League appearances for Tottenham so far this campaign, the teenager has created one chance, has a pass accuracy of 75% and a shot accuracy of 50%, and has won one dribble and one tackle.
Against Dortmund on Thursday evening, Onomah had a pass accuracy of 78%, put in one cross, attempted two dribbles, and made two interceptions, two clearances and two blocks.