Cook the Pasta: Boil salted water, add rotini pasta, and cook according to package instructions (8-10 minutes). Drain and rinse under cold water to cool.

Prepare the Bacon: Cook bacon in a skillet over medium heat until crispy (6-8 minutes). Transfer to a paper towel-lined plate and crumble once cool.

Make the Creamy Dressing: In a mixing bowl, combine mayonnaise and sour cream. Stir until smooth and adjust thickness with milk or buttermilk if necessary.

Combine the Ingredients: In the bowl with the dressing, add cooled pasta, crumbled bacon, diced tomatoes, and shredded lettuce. Carefully fold to coat.

Chill Before Serving: Cover and refrigerate for at least 15-30 minutes to meld the flavors together.