Start by soaking the cashews
Saute the onion for a few minutes in a large pan. Add the seasoning with a good pinch of salt. Stir until fragrant, about 30 seconds, then add the tomatoes.
Cook for just a couple of minutes then toss in the beans. Once warm, use a masher to go through and mash a bit up. Helps it thicken and its easier to spread on the tortilla.
Remove bean mix and wipe pan clean. Add a little oil and saute the veg with a pinch of salt for about 5 minutes until tender. Remove and wipe pan clean again.
While veggies are cooking you can add everything for the queso to a high-speed blender (Vitamix works amazing) and blend until smooth. Add more water, salt, and nutritional yeast as needed. You can also do this after you cook the veg if you don't like too many things going on at once.
Assemble the quesadillas by spreading some black beans (about 1/4 cup), then some veggies (about 1/2 cup), and some queso (start with a few tablespoons) over half a tortilla. Fold in half and cook a few minutes on each side. Top with anything you like, guacamole, hot sauce, salsa!