How to Make It
Preheat the oven to 500°. Prick the eggplants in a few places with a sharp knife. Bake them on 2 rimmed baking sheets until very soft, about 50 minutes.
Preheat the broiler. Broil the eggplants 3 inches from the heat until blackened on top, about 3 minutes. Let cool slightly. Slit the eggplant skins and scrape out the flesh, discarding as many seeds as possible. Finely chop the eggplants, transfer to a bowl and pour off any accumulated eggplant liquid.
Stir the garlic, olive oil, mint, minced preserved lemon peel, lemon juice and grated lemon zest into the chopped eggplant. Season with salt and pepper.
Put the cucumber in a colander set over a bowl and sprinkle with a large pinch of salt. Let stand for 10 minutes. Rinse the cucumber and pat thoroughly dry. Transfer to a bowl and stir in the yogurt and grated onion. Season with salt and pepper. Serve the cucumber raita and eggplant salad together, at room temperature.
Jarred preserved lemons are available at specialty shops and Middle Eastern markets.