Add oil to a large non stick pan over medium heat, then add scallions and garlic and cook for 5 minutes, until softened.
Add mushrooms and lime juice and cook until softened, about 5 minutes. Next, stir in spinach, corn, black beans, chili powder, cumin powder, salt, and pepper, and cook for another 5 minutes.
Remove vegetables from the pan and set aside. Add a tortilla to the pan and sprinkle some cheese on top. Then top with vegetable filling, more cheese, and another tortilla.
Press down gently with a spatula. Cook for 5 minutes, flip, and cook for another 5 minutes. Once the cheese is melty and the tortilla is lightly browned, the quesadilla is ready.