Cook pasta in salted water until tender, but just slightly underdone. While pasta cooks, place chopped red onion in the bottom of a strainer. Once pasta has just finished cooking, pour the boiling water over the onion through the strainer, and strain the cooked pasta. Rinse the pasta with cold water, and drain completely. Place the drained pasta and onion in a large bowl and allow to cool.
Add all remaining ingredients to the pasta mixture, and gently toss to combine. Garnish with fresh oregano or basil as desired.