Prep the veggies: Slice the bell pepper, zucchini, and red onion thinly. Rinse the black beans and spinach.
Heat the skillet: Heat a large skillet or griddle over medium heat and add 1 tsp of olive oil.
Sauté the veggies: Add the red onion, bell pepper, and zucchini to the skillet. Sauté for 3-4 minutes until they soften slightly. Season with chili powder, cumin, salt, and pepper. Add the spinach and black beans and cook for another 1-2 minutes until the spinach wilts.
Assemble the quesadillas: Lay a tortilla flat on a plate. Sprinkle ¼ of the shredded cheese evenly over half of the tortilla. Add a generous portion of the sautéed vegetables on top of the cheese, then fold the tortilla in half to cover the filling. Repeat for all tortillas.
Cook the quesadillas: Wipe the skillet clean and return to medium heat. Place each quesadilla in the skillet and cook for 2-3 minutes per side, until the tortilla is golden brown and the cheese is melted.
Serve: Slice each quesadilla into wedges and serve with salsa, guacamole, and sour cream on the side. Garnish with fresh cilantro if desired.
