In a large skillet over medium heat, cook bacon until crispy, about 6-8 minutes. Transfer to a paper towel-lined plate to drain and crumble once cool.

Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Drain and rinse under cold water to stop cooking; let cool completely.

In a small bowl, whisk together mayonnaise, sour cream, lemon juice, Dijon mustard, garlic, salt, and pepper until smooth.

In a large bowl, combine cooled pasta, crumbled bacon, tomatoes, and dressing. Toss gently until evenly coated. Fold in the chopped lettuce and chives just before serving to keep them crisp.