Boil Pasta: Cook the rotini in a large pot of salted boiling water according to package directions.
Blanch Broccoli: Exactly one minute before the pasta is done, add the chopped broccoli to the boiling water.
Drain and Rinse: Drain the pasta and broccoli together, then rinse thoroughly under cold water to stop the cooking. Shake off excess moisture.
Make Dressing: In a small bowl, whisk together the mayonnaise, Greek yogurt, apple cider vinegar, sugar, salt, and pepper.
Combine and Chill: Toss the pasta, broccoli, red onion, tomatoes, and cheese with the dressing. Cover and chill for 1 hour before serving.
