Bring a large pot of salted water to a boil. Cook the pasta until al dente, then drain and rinse under cold water to cool it quickly.

Place the bacon in a skillet over medium heat. Cook until crisp, then transfer to a paper towel-lined plate to drain. Crumble once cooled.

In a small bowl, whisk together the buttermilk, mayonnaise, lemon juice, chives, salt, and black pepper until smooth.

In a large mixing bowl, combine the cooled pasta, halved cherry tomatoes, chopped romaine, and crumbled bacon.

Add the diced avocado and pour the dressing over the salad. Toss gently until everything is evenly coated.