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.
Cut the bud end off of 12 of the lemons, and slice them in half crosswise. In a mixing bowl, toss the cut lemons generously with the salt and place in the sterilized jar. Juice enough lemons to completely cover the cut lemons with liquid. Pour the juice into the jar. Use a wooden spoon to gently press the lemons down into the jar. Secure the lid and let sit in a cool dry place for 1 week. It is important to shake the jar daily to redistribute the liquid and salt. After 1 week, top the jar off with olive oil and store in the refrigerator.
The lemons, can sit in the brine mixture longer than 1 week if desired, and will keep in the refrigerator for at least a year.
*The acid from the lemons may corrode a metal lid.
Yield: 1 quart