In a medium bowl, combine the yogurt, mayonnaise, and dressing mix. Refrigerate for at least 1 hour, or overnight.
In a large pot, cook pasta until al dente. Remove from heat, drain, and rinse under cold water.
Add tomatoes and bacon. Stir well to combine. Season with salt and pepper. Add lettuce and dressing just before serving so that it does not become too soggy. Serve immediately or refrigerate until ready to serve.
Notes
It's best to add the dressing to the salad right before serving so that it stays creamy.