Begin by cooking the rotini pasta in a pot of boiling water until it’s al dente, which should take about 8 to 10 minutes. You will know it is ready when it is tender but still firm. Test it for doneness but be careful not to overcook it as mushy pasta is not the goal. Drain the pasta in a colander and allow it to cool.
While the pasta cools, chop up the dill pickles into small pieces and finely dice the onion. Small pieces will mix better through the pasta and add flavor in every bite. Be cautious with the onion; if it is too large, it might overpower the salad.
In a small bowl, stir together the mayonnaise, sour cream, and 1/3 cup dill pickle juice for a creamy dressing. This will tie everything together and you will notice the rich aroma of dill as you mix in the fresh or dried dill. Ensure the dressing is smooth without lumps for the best finish.
In a large mixing bowl, combine the cooled pasta with the chopped dill pickles, diced onion, and dressing. Gently mix everything together, making sure the pasta is coated nicely with the dressing. Take care to avoid breaking the pasta apart by over-mixing.
Add salt and pepper to taste. Cover the salad and refrigerate for at least two hours. This chilling time allows the flavors to deepen. Just remember, letting it sit too long may dry it out, so monitor your salad. If it seems dry after chilling, adding a tablespoon or two of pickle juice can help restore some moisture and freshness.