1. Whisk together vinegar and 1 Tbsp. sugar in a bowl. Add onion, and let stand 30 minutes; drain, reserving 2 Tbsp. vinegar mixture.
2. Prepare pasta according to package directions.
3. Place chopped tomatoes and next 9 ingredients in a serving bowl. Add hot cooked pasta, onion, and reserved vinegar mixture, gently tossing to combine. Sprinkle with peanuts. Serve immediately, or cover and chill up to 24 hours.
Note: For testing purposes only, we used Mueller's Whole Grain Spaghetti.