1. Cook the pasta: Bring a large pot of salted water to a rolling boil. Add your chosen small pasta and cook according to package directions until al dente. This usually takes about 8-10 minutes. The pasta should be tender but still have a slight bite.

2. Drain and cool the pasta: Once cooked, drain the pasta thoroughly in a colander. Rinse it under cold water for about 30 seconds to stop the cooking process and cool it down quickly. This prevents the pasta from becoming mushy and helps the salad stay fresh. Let it drain completely.

3. Prepare the dressing: While the pasta is cooking, in a large mixing bowl, combine the mayonnaise, Greek yogurt, fresh lemon juice, lemon zest, black pepper, and salt. Whisk these ingredients together until the dressing is smooth and well combined. Taste and adjust the salt and pepper if needed.

4. Add the tuna and vegetables: To the dressing bowl, add the drained tuna, breaking it up gently with a fork. Stir in the finely diced red onion and celery. These add a crucial crunch and fresh flavor to the salad.

5. Combine all ingredients: Add the cooled and drained pasta to the bowl with the tuna mixture. Gently fold everything together until the pasta is evenly coated with the dressing and all the ingredients are well distributed. Be careful not to overmix, which can break down the pasta.

6. Stir in fresh parsley: Finally, stir in the chopped fresh parsley. This adds a burst of color and a fresh, herbaceous note to the salad.

7. Chill before serving: For the best flavor and texture, cover the bowl and refrigerate the pasta salad for at least 30 minutes to allow the flavors to meld. A longer chill time (1-2 hours) is even better.

8. Serve and enjoy: Give the salad a final stir before serving. If it seems a little dry after chilling, you can add another tablespoon of mayonnaise or a splash of lemon juice to loosen it up.