Add all the dressing ingredients to a small bowl and whisk to combine. Add in the finely chopped onion. Set aside.
Cook the rotini pasta until al dente. Drain the water. Place the colander with pasta in a bowl filled with ice-cold water. Let it cool for a few minutes.
Cut the tomatoes, cucumber, mozzarella, salami, and olives into small pieces. Chop the parsley leaves. Add everything to a large bowl. Add in the drained cool pasta. Pour in the dressing and stir to combine.
To make the dish more flavorful place the salad in the fridge for at least half an hour.
