Newcastle won the Wednesday night via goals from Nick Woltemade, Anthony Gordon (2) and Harvey Barnes.
Howe said afterwards: "I ask for a lot - there is never one thing. If you were to pin me down to one, it would be 100% effort in every moment.
"And tactically the way we are set up is complex, I ask loads of different thing. But the effort has to be there.
"I think it has been there this season, I don't have a feeling it hasn't been there.
"You can question how well we performed in certain moments of course and we will continue to strive for more. But I do see a group that is committed and trying their best."
Howe continued: "I thought it was a really good display. It was always going to be a tough game, but as soon as we got that first goal I thought we were going to play very well.
"I thought we attacked well and defended well. Any time you get a clean sheet in the Champions League, that is a good statement to make.
"Generally, the way we attacked there was a feeling we could score at any moment.
"Two of the goals came from penalties, but there were some good individual performances as well."