Cook pasta until al dente; drain, rinse with cold water, and set aside.
Drain and flake tuna; dice celery, bell pepper, and onion; thaw peas.
Whisk mayonnaise, yogurt, vinegar, mustard, lemon juice, sugar, salt, pepper, and dill for dressing.
Combine pasta, tuna, celery, bell pepper, onion, peas, and parsley in a bowl; add dressing and toss.
Refrigerate for 30 minutes, then serve chilled.