In a large serving bowl, combine the kohlrabi and apple matchsticks.
Add the cheese, if using, and the tarragon leaves and sunflower seeds.
Sprinkle lemon zest liberally over the bowl.
Drizzle in 1 tablespoon olive oil and 1 tablespoon lemon juice, then sprinkle lightly with salt and black pepper.
Use your hands to gently toss the salad, then add another drizzle of olive oil and lemon juice if the salad seems dry.
Finish with another light sprinkle of salt and pepper and serve immediately.