Poppy Seed Dressing

3 tablespoons chopped onion
1/3 cup vinegar
1 1/2 cups granulated sugar
2 teaspoons dry mustard
2 teaspoons salt
1/3 cup vinegar
2 cups vegetable oil
3 tablespoons poppy seeds

In a blender, blend onion and vinegar until completely smooth. Add sugar, dry mustard, salt, and vinegar. Mix at medium speed until well combined. Add vegetable oil (never use olive oil) very slowly and continue to mix with blender until thick. Add poppy seeds and continue to mix until blended.