Bring a large pot of salted water to a rolling boil. Add the rotini and cook for about 8-10 minutes until al dente. Drain and rinse under cold water. Set aside in a large mixing bowl.

In a skillet over medium heat, cook the bacon until crispy, about 6-8 minutes. Turn occasionally for even cooking. Let cool and chop into pieces.

In a mixing bowl, combine mayonnaise and milk or buttermilk. Whisk until smooth and adjust seasoning with salt and pepper.

Fold in the crispy bacon pieces and chopped tomatoes into the cooled pasta. Pour the dressing over and stir until well-coated.

Just before serving, fold in the chopped lettuce to maintain its freshness.

Cover the salad and refrigerate for 15-30 minutes to meld flavors.