Boil the pasta in a large pot of salted water according to the package directions for al dente.
Blanch the chopped broccoli by adding it to the boiling pasta water during the final 60 seconds of cooking.
Drain the pasta and broccoli together, then rinse immediately under cold water to stop the cooking process.
Whisk the mayonnaise, sour cream, apple cider vinegar, sugar, salt, and pepper in a large bowl to create the dressing.
Toss the cooled pasta, broccoli, cherry tomatoes, and red onion into the dressing until completely coated. Chill before serving.
