In a medium saucepan over medium heat, steam mushrooms, cumin, onion powder, 1 tablespoon of broth, and 2 tablespoons of lemon juice.
Steam for about 10 minutes, stirring occasionally.
Drain steamed mixture and set aside, reserving the liquid in the pot.
To the pot, add the watercress and chopped onion.
Saute for 2 minutes.
Add the remaining broth and 1/2 of the mushroom mixture; simmer for another 10 minutes.
In a blender, place the mixture, tofu, parsley, and the remaining lemon juice; puree the mixture.
Place the pureed mixture back in the pot, add the remaining mushrooms and reheat.
Serve hot.