Cook the whole wheat pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large mixing bowl, combine the Greek yogurt, mayonnaise, Dijon mustard, lemon juice, garlic powder, onion powder, black pepper, and salt. Mix until smooth and creamy.
Add the drained tuna to the bowl and gently break it apart with a fork.
Stir in the cooled pasta, cherry tomatoes, cucumber, red onion, and parsley. Mix until all ingredients are well combined and coated with the dressing.
Taste and adjust seasoning with additional salt or pepper if needed.
Cover and refrigerate for at least 30 minutes to allow the flavors to meld. Serve chilled.