You can use Trader Joe's pre-cooked lentils for this hearty summer salad. If you can't find them, substitute about 3 cups cooked lentils. You can change this recipe for the seasons by omitting the eggplant and adding other fresh ingredients.
For the dressing: Place the vinegar, 1 tablespoon lemon juice, the mustard, syrup and olive oil in a jar. Season with salt and pepper. Cover the jar and shake vigorously until blended. Set aside. This can be done ahead.
For the salad: Preheat the oven to 425°. Toss the eggplant and onions with 2 tablespoons olive oil; season with salt and pepper. Spread out in one layer on an oiled baking sheet. Place in the oven and roast for about 20-25 minutes, shaking the pan and flipping the eggplant after 15 minutes, until golden brown.
Rinse the lentils in warm water and lightly separate any clumps. Place in a bowl with the eggplant and onions. Toss with the dressing, and stir in the walnuts and parsley. Season to taste, adding more lemon juice, if needed.