Meanwhile, slice 1 lemon into 1/8-inch-thick rounds. Combine sliced lemon, 2 cups water and 2 tablespoons kosher salt in small saucepan; bring to boil. Reduce heat and simmer until lemon slices are tender, about 10 minutes. Drain lemons, then very coarsely chop. Cut remaining lemon in half and squeeze out enough juice to measure 2 tablespoons. Mix chopped lemons, 2 tablespoons lemon juice, white balsamic vinegar and oil in small bowl. Coarsely crush cumin and coriander seeds using mortar and pestle (or wrap in foil and pound firmly using rolling pin). Mix seeds into lemon dressing. Season to taste with pepper.