If your salsa is already made, this bean-cheese-spinach (use frozen spinach) combo takes 10 minutes to fix.
Spread beans over half of each tortilla. Top with spinach and cheese; season generously with salt and pepper. Fold tortillas in half over fillings.
When it's time to eat, place quesadillas on a microwave-safe plate; cook on high power until heated through, about 2 minutes. Top with salsa.
Night before: Assemble the quesadillas, place in a portable container, and put in the fridge. Using frozen spinach saves on cooking time.