Cook pasta: Bring a large pot of water to a boil and cook the pasta according to package instructions until tender, about 10 minutes—you’ll see the noodles swell and feel firm but not stiff.
Rinse pasta: Drain the hot water, then run cold water over the noodles until they’re cool. Shake off excess water thoroughly to prevent a watery dressing and sticky noodles.
Whisk dressing: In a medium bowl stir together Greek yogurt, mayonnaise, relish, sriracha, apple cider vinegar, salt and pepper until smooth and evenly colored. Taste and tweak the seasoning or hot sauce to your liking.
Combine ingredients: In a large bowl toss the pasta with tuna, bell pepper, carrot, celery and red onion. Pour in the dressing and stir gently until everything is well coated with the creamy mixture.
Chill salad: Cover the bowl and refrigerate for at least an hour. Letting it rest gives the flavors time to blend, and you’ll serve it cold and refreshing.