What a great surprise... peaceful atmosphere, air-conditioned, spotless. I was only going to get momos but the plate of the day looked so good, so I went for it: fantastic! The momos were also superb and once you've tried them you'll probably be back for more.
Regarding comments about the blandness, note that, as in many Portuguese restaurants, you have to specially request the hot sauce (which is often homemade). This place has an absolutely killer—and spicy—house concoction with habaneros. They were even nice enough to give me extra for my takeaway.
Highly recommended, this place adds a nice bit of diversity to Lisbon's already great vegetarian offerings.