Heat 2 tablespoons of the olive oil in a medium-size sautÈ pan over high heat. Add the onions, season with salt and pepper, and cook, stirring often, until they caramelize, 8 to 10 minutes. Add the garlic, parsley, and vinegar and cook, stirring, for about 1 minute. Set aside.
Combine the grilled vegetables in a medium-size mixing bowl and season with salt and pepper. Divide the mixture into 4 equal portions and spread on 4 of the tortillas, leaving about a 1-inch border all around. Sprinkle the vegetables with equal amounts of the cheese, then top with the remaining tortillas. Gently press the edges together to seal.
Heat 1 teaspoon of the olive oil in a large non-stick skillet over medium-high heat. Carefully lay a quesadilla in the center of the skillet and cook until lightly browned, about 1 minute. Then, with a wide spatula, turn the quesadilla over and cook until lightly golden, 1 to 2 minutes. Repeat the procedure using the remaining oil.
To serve, cut the quesadillas into 4 wedges. Arrange on individual plates and top with the onion marmalade and cilantro sour cream.
Yield: 4 servings