Cook the pasta in well-salted water to al dente according to the package instructions. Drain in a colander, then rinse with cold water to stop the cooking. Shake off as much water as possible. Let the colander with the pasta sit in the sink or on a towel to continue draining while you prepare the rest of the salad.
Place the red onion in a small bowl and cover with cold water. Let sit at least 5 minutes, then drain and pat dry.
In a small bowl or large measuring cup, whisk together the dressing ingredients: Greek yogurt, lemon zest (zest it right into the bowl), lemon juice, honey, Dijon, salt, oregano, and pepper.
In a large serving bowl, place the cherry tomatoes, sun-dried tomatoes, bell pepper, onion, capers, and parsley.
Shake the pasta once more, then add it to the bowl.
Top with the dressing and stir gently to combine.
Flake the tuna into the bowl in big pieces, then toss gently to combine. Taste and adjust the seasoning as desired (depending upon your tuna, you may need a few additional good pinches of salt).
For the best taste, refrigerate at least 1 hour before serving to allow the flavors to marry and develop. Enjoy directly from the fridge or at room temperature.
*You can use either dry-packed or oil-packed sun-dried tomatoes. For dry-packed, rehydrate them by covering them with very hot water and letting soak for 5 minutes, then drain and pat dry. For oil-packed, use a paper towel to blot of excess oil first.
TO STORE: Refrigerate leftover pasta salad in an airtight storage container for up to 2 days.