Lisbon now has a lot of vegan restaurants, but this one is the best one that I tried. I was there with my girlfriend, we both tried the burger served with sweet potato and vegan sauce and was with any question the best combination that I've tried ever.
Special atmosphere, very relaxed, people are always fiendly there. The restaurant is located in Chiado, outside of the touristic area. You have to book in advance, it's always full because of its quality.
The burger there served with sweet potato is amazing!