Cook pasta until tender, but just slightly underdone. While pasta cooks, place chopped red onion and corn kernels in the bottom of a strainer. Once pasta has just finished cooking, pour the boiling water over the onion and corn through the strainer, and strain the cooked pasta. Place the drained pasta, onion, and corn in a large bowl and allow to cool.
Add all remaining ingredients to the pasta mixture, and gently toss to combine.
In a smaller separate bowl, stir together skinny ranch dressing. Fold the dressing into the pasta salad.