Bring a large pot of salted water to a boil. Add the pasta and cook until al dente according to package directions, about 8-10 minutes. Drain and rinse under cold water; set aside.
Heat a skillet over medium heat. Cook bacon slices until crisp, about 6-8 minutes, turning as needed. Drain on paper towels and chop when cooled.
In a medium bowl, whisk together mayonnaise, sour cream, and buttermilk. Add garlic powder, onion powder, dill, parsley, dried chives, lemon juice, salt, and pepper. Mix well and adjust seasoning.
Prepare vegetables by halving cherry tomatoes, chopping romaine lettuce, and slicing green onions thinly.
In a large bowl, combine cooled pasta, bacon, tomatoes, lettuce, green onions, and shredded cheddar cheese. Pour dressing over and gently toss to coat evenly.
Cover the salad and refrigerate for at least 20 minutes to meld flavors. Toss again before serving and adjust seasoning if needed.