Cook the elbow macaroni in a large pot of boiling salted water according to package instructions until al dente. Drain the macaroni in a colander and rinse under cold water to cool. Set aside in a mixing bowl.
In a skillet, cook the strips of bacon over medium heat until crispy. Remove the bacon from the skillet, crumble it, and set aside.
In the mixing bowl with the cooled macaroni, add the halved cherry tomatoes, chopped romaine lettuce, crumbled bacon, and green onions if using.
In a separate bowl, whisk together the mayonnaise, sour cream, apple cider vinegar, Dijon mustard, salt, and pepper until well combined.
Pour the dressing over the macaroni-salad mixture and gently stir until everything is well coated.
Taste and adjust seasoning if needed, then cover and refrigerate for at least 30 minutes before serving to let the flavors meld.
For added flavor, consider including diced avocados or shredded cheese as a mix-in.
Serve chilled for the best flavor.