Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Drain and rinse with cold water to stop the cooking process. Set aside to cool.
In a large mixing bowl, whisk together the mayonnaise, yogurt, and Dijon mustard until smooth. Season with salt and pepper to taste.
Add the cooled pasta, tuna, cherry tomatoes, red onion, and pickles to the bowl with the dressing. Toss gently until everything is well coated.
For the best flavor, let the salad chill in the fridge for at least 30 minutes. Just before serving, garnish with chopped chives.
