In a small mixing bowl, whisk together ranch seasoning packet, milk and mayonnaise. Refrigerate to thicken up while prepping the rest of your salad.
Cook pasta according to package instructions, drain and rinse with cold water.
In a large bowl, combine pasta, crumbled bacon, cherry tomatoes, chopped lettuce and diced red onion. Pour over about 1/2 of the dressing and gently fold to coat evenly. Add more or less, to taste. Season with salt and pepper to taste.
If refrigerating salad to eat later, reserve extra dressing to add on right before serving.