In a large bowl, whisk together the mayonnaise, mustard, vinegar, lemon juice, dill, garlic powder, onion powder, salt, pepper, and sugar until fully combined and smooth. This creates your flavor foundation—I like to taste a small spoonful at this stage to ensure the balance of tangy, savory, and herbaceous flavors feels right to you before adding the other ingredients.

Bring a large pot of salted water to a boil and cook the pasta according to package directions until just al dente. Drain the pasta thoroughly, then rinse it under cold running water until completely cooled—this stops the cooking process and prevents the pasta from becoming mushy when mixed with the creamy dressing. Make sure to drain well so excess water doesn't dilute your dressing.

While the pasta cooks, dice the celery into small, uniform pieces, finely mince the red onion, and shred or grate the carrots. Having all your vegetables prepped and ready ensures the assembly step moves smoothly and helps the flavors distribute evenly throughout the salad.

Add the cooled pasta from Step 2, flaked tuna, peas, and the fresh vegetables from Step 3 to the dressing base from Step 1. Using a large spoon or spatula, gently fold everything together until all components are evenly coated with the creamy dressing. I find that folding rather than stirring vigorously helps keep the tuna in larger, more appealing pieces instead of breaking it into tiny bits.

Transfer the salad to a serving bowl or storage container and refrigerate for at least 30 minutes before serving. This chilling time allows the flavors to meld together and creates a more pleasant eating temperature. The salad actually tastes better the next day as the flavors continue to develop, so feel free to make it ahead.