Begin by bringing a large pot of salted water to a rolling boil. Add garden rotini pasta and cook according to the package instructions, typically about 8-10 minutes, until al dente. Stir occasionally to prevent sticking. Once cooked, drain the pasta in a colander and let it sit for a moment to steam off excess moisture.

Transfer the drained rotini pasta to a large bowl and rinse it under cold running water for 2-3 minutes. This stops the cooking process and cools the pasta down quickly, ensuring your creamy pasta salad won’t become soggy later.

In a separate large mixing bowl, combine mayonnaise, Italian vinaigrette dressing, Cajun seasoning, ground black pepper, and white sugar. Whisk these ingredients together until you have a creamy and well-blended dressing.

Now, add the cooled pasta to the dressing mixture, followed by the chopped red onion, diced cucumber, halved grape tomatoes, and diced yellow bell pepper. Gently fold everything together with a spatula until all the ingredients are evenly coated.

Once mixed, cover the bowl tightly or transfer to an airtight container and refrigerate for 1-3 hours, allowing the flavors to meld together.

When ready to serve, spoon the chilled creamy pasta salad into a large serving bowl or individual plates. Offer a sprinkle of additional Cajun seasoning on top for an extra kick, if desired.