Spray a large griddle or skillet with cooking spray and heat over medium heat.
Working in batches as necessary, place one tortilla on the griddle and spread with ¼ cup squash. Sprinkle with ¼ cup cheese. Add a quarter of the black beans and drizzle with about 3 tablespoons of salsa. Top with another ¼ cup cheese and finish with a tortilla.
Heat 5 minutes per side or until browned and crispy as desired. Transfer to a plate and use a pizza cutter to slice into wedges. Serve hot with sour cream, avocado, and lime.