Cut each eggplant lengthwise into 5 mm thick slices and sprinkle with salt. Weight for 1 hour.
Make the sweet-and-sour sauce by simmering tomato sauce with sugar, vinegar, and pepper.
Preheat oven to 220°C. Trim prosciutto, cut mozzarella, and bake eggplant slices.
Top each eggplant slice with prosciutto and cheese, roll up, and place seam-side down on a platter.
Spoon over remaining sauce, scatter with basil, and optionally add pine nuts and preserved lemon.
