Bring a large pot of salted water to a rolling boil. Add the rotini pasta and cook according to package directions until al dente. Drain well in a colander and rinse with cold water to stop cooking and cool down. Transfer to a large mixing bowl and toss with 1 tablespoon of olive oil (optional) to prevent sticking. Set aside to cool completely.

While the pasta is cooking and cooling, drain the canned tuna thoroughly and flake it into small pieces. Dice the celery, red onion, and bell pepper into small, uniform pieces. Chop the fresh parsley and dill.

In a small bowl, whisk together the mayonnaise, Greek yogurt, fresh lemon juice, Dijon mustard, minced garlic, salt, and black pepper until smooth and well combined. Taste and adjust seasonings if necessary.

Add the flaked tuna, diced celery, red onion, bell pepper, chopped parsley, and chopped dill to the large mixing bowl with the cooled pasta.

Pour the creamy lemon-dill dressing over the pasta and tuna mixture. Gently toss everything together until all ingredients are evenly coated.

Cover the bowl and refrigerate the Tuna Pasta Salad for at least 30 minutes, or preferably 1-2 hours, to allow the flavors to meld. Stir well before serving.