Yes, soup. This is no small deal. Portuguese soup is one of the unknown treasures of the world.
It's nutritious, low fat and absolutely delicious. No cream here, but it's lip-lickingly scrumptious and a great way of filling up on low cal veggies before a main meal and practically getting your "five-a-day" in a single bowl.
Some of my favourites are: Caldo Verde (literally green soup, but it's kale and potato with Portuguese saiusage), Sopa de Abóbora (pumpkin soup), Sopa de Agrião (watercress soup) and Sopa de Feijão Verde (green bean soup).
For something heartier try Sopa de Feijão (bean soup - usually kidney beans), or Sopa de Grão (chick pea soup).
Order soup in a café or restaurant and you are unlikely to spend more than a couple of euros for a nutritious lunch. It always was poor man's food but it's rich pickings as far as I'm concerned.
Find some recipes here. Enjoy!