For the Korean sauce: Add the cashews, 2 cups water, olive oil, tamari and lime juice to a blender. Blend on high speed for 2 minutes, until smooth.
For the fresh salsa: In a mixing bowl, combine the tomatoes, jalapenos, onions, cilantro lime juice, 1 tablespoon salt and 1 teaspoon black pepper. Mix well.
For the cactus: Fill a medium soup pot halfway with water and bring to a boil. Add the cactus, lower the heat to medium low and cook for 15 minutes. Turn off the heat, add 1 tablespoon salt and let sit for 5 minutes. Drain the cactus; when cool enough to handle, cut into dice.
Heat the oil in a large skillet over medium-high heat. Add the cactus and cook undisturbed until golden, about 3 minutes. Stir and cook for 2 more minutes, until light golden all over.
Stir 2 tablespoons of the Korean sauce into the skillet; let cook for 1 minute.
For the tacos: Divide the cactus mixture among the tortillas. Top each with some cabbage and 1 tablespoon of the fresh salsa. Garnish with watercress and serve.
Edible cactus is sold in many Latin markets, where it is often cleaned and diced (so you don't have to deal with the thorns!).
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.