Prepare pasta according to package directions, removing the pasta from the heat about one minute before directions say. Remove ½ cup pasta water for later use, if necessary.
Drain pasta in a strainer and give a quick rinse under the cool water to mostly stop the cooking process. Put warm pasta in a large bowl for mixing. Alternate pouring ¼ cup dressing over warm pasta, stir, add another ¼ cup, stir, until the pasta is coated to your taste.
Add prepped onions, tomatoes and olives and use your hands or a big spoon to gently mix all the vegetables through the pasta. Check for moisture – do you want any extra dressing? Add it now while pasta is a little warm.
Chill the pasta for about 30 minutes then stir in crumbled feta. Because it has been slightly chilled, the cheese won’t melt. If you have longer to chill, great! You can add cheese right before it’s served.
Before serving or packaging for delivery, give it a good stir and taste. Need dressing? Salt? Add in SMALL amounts and test after each addition.