Begin by bringing a large pot of salted water to a rolling boil. Add the rotini pasta and cook according to the package instructions, usually about 8-10 minutes for al dente. Once cooked, drain and rinse the pasta thoroughly under cold running water.

While the pasta cools, heat a large skillet over medium heat. Add the bacon pieces and cook them until crispy, about 5-7 minutes. Transfer the bacon to a paper towel-lined plate to absorb excess grease.

In a mixing bowl, blend together the mayonnaise, sour cream, and milk until smooth. Adjust the consistency with more milk if necessary.

In a large mixing bowl, combine the cooled rotini pasta, crispy bacon, and diced tomatoes. Pour the prepared dressing over the mixture and gently toss until well combined.

Just before serving, gently fold in the washed and dried lettuce to maintain its crispness.

To enhance the flavors, cover the salad and refrigerate it for at least 15-20 minutes before serving.