Cook pasta according to package directions. While pasta cooks, place chopped red onion in the bottom of a strainer. Once pasta has cooked, pour the boiling water over the red onion through the strainer, and strain the cooked pasta. Place the drained pasta and red onion in a large bowl and allow to cool.
In a smaller separate bowl, stir together BBQ sauce, sour cream, chives, cilantro, pepper, onion powder, garlic powder, and thyme and pour over pasta. Toss to mix.
Add all remaining ingredients, and stir to combine. Garnish with additional shredded cheddar and chives or cilantro as desired. Refrigerate until ready to serve.