Begin by bringing a large pot of salted water to a boil. Add the whole wheat rotini pasta and cook according to package directions, about 8-10 minutes, until al dente. Drain and rinse under cold water.

In a large mixing bowl, combine the cooled pasta with cucumber, celery, red bell pepper (or cherry tomatoes), and cooked peas. Fold in the drained canned tuna, breaking it into bite-sized pieces.

In a separate bowl, whisk together the Greek yogurt, light mayonnaise, lemon juice, and Dijon mustard until smooth. Add dill, garlic powder, salt, and pepper; mix until combined.

Pour the dressing over the salad mixture and fold gently to coat evenly. Make sure not to break down the vegetables and pasta.

Cover and refrigerate for 20-30 minutes to meld the flavors. Stir before serving and adjust seasoning as needed.