Spurs meet Manchester United and Mbeumo in today's early kickoff.
At Brentford, Frank and Mbeumo worked together for six years before both men left the Bees this summer.
"He is a very good player. He’s playing for Man United, and I’m very happy for him," Frank laughed when asked about trying to sign the Cameroon international.
"When you work with a player for six years, you get a close relationship. To see him develop from being a young man, 19-years-old when he moved to London and left six years later, going into one of the biggest clubs in the world with all that focus and the way he stepped up.
"For me, looking from the outside, maybe a little bit biased, I think he's been their best offensive player. He can create, he can score, he works hard, he's a team player. He's the perfect example of a player who is confident but humble. He's a top player."
He added: "He’s close to being the complete winger. He’s got pace, he can dribble, he can cross the ball, he can score goals, he can arrive in the last line, he works incredibly hard. He’s a good team player."
"I think he will have fantastic success there. I hope that for him, not tomorrow, but in general I wish him all the best."