How to Make It
Cook pasta according to package directions, omitting salt and fat; drain. Cool about 10 minutes.
Meanwhile, stir together mayonnaise, yogurt, dill, lemon juice, water, mustard, salt, pepper, and garlic in a large bowl until thoroughly combined.
Fold cooled pasta, celery, peas, and tuna into mayonnaise mixture until thoroughly coated. Serve at room temperature or chilled. Garnish with more dill.