Cook the Pasta: Bring a large pot of salted water to a boil, add the rotini, and cook for about 8-10 minutes until al dente. Drain and rinse under cool water. Set aside to cool.

Prepare the Vegetables: In a large bowl, add chopped cucumber, celery, red bell pepper, and cooked peas. Stir to combine.

Combine the Tuna: Add the drained tuna to the vegetable mix and gently fold to combine without breaking the tuna too much.

Make the Dressing: In a separate bowl, whisk together Greek yogurt, mayonnaise, lemon juice, and mustard until smooth.

Season the Dressing: Stir in chopped dill, garlic powder, salt, and pepper until well combined.

Combine Everything: Pour the dressing over the salad and gently toss to coat the ingredients.

Chill for Flavor: Cover and refrigerate for 20-30 minutes to allow the flavors to meld.

Serve and Enjoy: Serve chilled, and pair with grilled chicken or fruit salad.