In a small bowl, combine the vinegar, preserved lemon juice, and cumin seeds. Slowly whisk in the olive oil until it is all incorporated. Adjust seasonings with salt and pepper, to taste.
Place tomato wedges in a separate bowl. Season the tomatoes with the preserving brine, and additional salt and 1/2 teaspoon pepper. Add the chopped lemon rind, cilantro, parsley, and red onions, tossing to coat well. Taste and adjust seasoning with salt and pepper as needed. Drizzle a small amount of the dressing over the tomato mixture and toss to combine.
Arrange lettuce on 4 salad plates. Top with equal amounts of the tomato mixture and drizzle with additional dressing, if desired. Serve immediately.
Yield: 4 servings