Bring a large pot of salted water to a boil and cook the shell pasta according to package directions until al dente—this usually takes about 8-10 minutes. Drain the pasta thoroughly in a colander and set aside to cool slightly. I always use Barilla because it holds its texture perfectly in a cold salad and doesn't get mushy.

While the pasta cooks, finely dice the celery ribs into 1/4-inch pieces and mince the red onion. Drain and flake the tuna into small, bite-sized pieces, breaking up any large chunks. Measure out the peas—if using frozen, no need to thaw them as they'll be incorporated cold. Keep these ingredients separate until assembly.

In a separate bowl, whisk together the mayonnaise, Greek yogurt, and Dijon mustard until smooth and well combined. This mixture creates a lighter, tangier dressing than mayo alone while still maintaining that classic creamy flavor. I prefer Hellmann's mayo because it gives a richer, more authentic taste that balances perfectly with the Greek yogurt's tang.

In a large bowl, combine the cooled pasta from Step 1 with the diced celery, red onion, peas, and flaked tuna. Pour about half of the dressing mixture from Step 3 over the pasta and vegetables, then sprinkle with salt, pepper, and fresh dill. Toss everything together gently but thoroughly to coat all ingredients evenly with the dressing.

Cover the salad and refrigerate for at least 30 minutes so the flavors can meld together and the pasta can absorb the dressing properly. Just before serving, stir in the remaining dressing from Step 3 to freshen up the salad and ensure it has the right creamy consistency. The pasta will have absorbed quite a bit of moisture during resting, so the second addition of dressing keeps it from drying out.