Heat 1 tablespoon oil in a medium pan over medium-high heat. Add the oil, bell peppers, black beans, corn, onion, garlic, cumin, chili powder, salt, and pepper. Season with salt and pepper and cook for 3-4 minutes or until the bell peppers and onions of softened. Turn off heat and stir in the cilantro.
Arrange 2 tortillas on a sheet pan. Top with cheese, cooked veggies mixture, and another layer of cheese. Cover with remaining tortillas.
Bake for 10 minutes or until tortillas are crisp and the cheese is melted.
While baking, make the sour-cream cilantro sauce. Whisk all the ingredients in a medium bowl until combined.
Place quesadillas on a cutting board. Cut into wedges. Enjoy with sour cream cilantro sauce!