Soak raw cashews overnight in enough water to cover them or for a few hours prior to using. For a quick soak cover with boiling water for 2 hours. (If you have a vitamix you can omit this step completely if you've 'run out of time'.) Drain and rinse the cashews and put them in the blender with ½ to 1 cup of water, lemon juice, apple cider vinegar and salt and blend until completely smooth. refrigerate until serving.
Clean the portobellos by scraping out gills and remove stems with a small spoon. Slice into 1/4 inch pieces. Thinly slice peppers and onions.
Mix all the marinade ingredients together.
Add cut mushrooms to one large flat baking dish and peppers/ onion to the other. Set the pepper/ onion mix in the fridge until later.
Toss the mushrooms well with about ¾ of the marinade. Set the remaining ¼ of the marinade aside for later. Leave the mushrooms marinating for at least half an hour (preferably longetossing every 30 minutes as able. Cover and refrigerate.
When you're ready to eat, toss the pepper mix with the remaining marinade. Preheat a large skillet and pour in contents of the bowl containing peppers/onions/ marinade. Saute over medium for about 10 minutes or until veggies are softened.
Meanwhile preheat a grill pan over med or high heat. Lay the marinated mushrooms on the pan and grill 3-5 minutes per side until they have nice char lines.
Warm tortillas in a separate skillet.
Place tortilla on a plate and layer with mushrooms, pepper/onion mix, cashew cream, guacamole or avocado if using, cilantro and any other desired toppings.