Add onion, vinegar, sugar, mustard, pepper and salt to blender or food processor. Blend until pureed and there are no large chunks
Once everything is pureed with the food processor running, drizzle in the oil through the hole in the top of the blender or food processor. Mix until dressing is creamy.
Salad
Add all your salad ingredients to a bowl and toss lightly with dressing. Serve.