Bryan Mbeumo had the Bees ahead before Vangelis Pavlidis struck an equaliser in front of a full Estadio da Luz.
Frank later said, “It’s a great experience for everyone. The Premier League is the best league in the world, we are privileged to play in it, but sometimes we don’t think or talk enough about the other countries or clubs.
“Benfica is a huge club, I don’t know if we really understood that, but we come to this fantastic stadium and they bring over 40,000 to a friendly - it’s impressive.
“It was another good test against another good opponent. I thought we started the game very well, until they equalised I felt we were more on top of the game.
“The second half started slow but we grew into it; the last half-hour, we played with a very young team - well done to them and to everyone who has been involved in their development. What a great experience for them today.”