Heat a medium-size nonstick skillet over medium heat. Place a tortilla in the skillet and warm it 2 to 3 minutes. Turn the tortilla in the skillet and place half of the tomatoes, bell pepper, green onion, and carrots on one half of the tortilla. Top the vegetables with half of the cheese, yogurt, salsa, and spinach. Fold the tortilla over the filling and cook another 3 minutes, or until the cheese melts.
Transfer the quesadilla to a plate, cover it with foil to keep it warm, and make another quesadilla in the same fashion.