Vegan Cheese - Use your favourite mozza / spicy shredded cheese or here's a recipe for a delicious Jalapeno cheese you can make at home (Make this a few days ahead of time). Cashew Cream - optional, but I think makes a wonderful addition. Recipe here but these are the ingredients you will need (½ cup cashews, water, salsa, garlic, cumin, lime, salt). If you have a high-speed blender like a Vitamix, this takes only a few minutes to make (you can do it while the filling is cooking). The Filling - Heat 1 tbsp of oil in a large stirfry pan over medium-high heat. Add chopped onions and sweet potato or squash - cook, stirring as necessary until the squash is softening and the onions are fragrant, after about 4 minutes, add in the chopped peppers stirring to incorporate. Add the garlic and continue to cook for another 4 - 5 minutes (adjust the heat if necessary).
Add the canned tomatoes and its juice (either break the tomatoes up with the back of a spoon, cut them or gently break them with your hands before you put them into the pan).
Add the salsa and all the spices - bring to a boil and then reduce the heat to low and simmer uncovered for about 10 - 15 minutes to let the juices thicken.
Stir in the black beans, kidney beans, and corn (if using).
Taste and adjust seasonings - then remove from heat.
Putting It All Together - Spray a 13x9 lasagna pan, cover the bottom of the pan with a layer of overlapping corn tortillas (I've used flour/ancient grain tortillas or even cooked lasagna sheets successfully when I'm out of corn tortillas - the non-corn variety of tortillas can become a bit soggy though - but work in a pinch). Spread with ½ the bean mixture, dollop ½ the cashew cream on top and gently spread it over bean mixture. Repeat with another layer of tortillas, the remaining bean mixture and swirl in any remaining cashew cream.
Cheese it Up! - Top with 12 evenly spaces slices or shredded piles of your favourite vegan cheese and place covered in a pre-heated 350º F oven for 30 minutes.Remove the foil, increase the temperature to 375º F and cook for 5-10 more minutes. Sometimes, I broil for a few minutes at the end if the cheese is being non-compliant! Remove from the oven and set aside to cool for 10 minutes.
Optional Toppings (but not really) - Meanwhile, slice (or chop) the tomatoes, green onions, olives, and avocado and place in serving dishes. As well pass any remaining cashew cream or vegan sour cream and hot pepper flakes along side the optional toppings.